How do I tighten the belts on my 1991 toyota landcruiser to keep from making any slipping noise? Belt only slips when I'm turning sharp in either direction.

Sounds like the belt tightener unit is wore out and needs replacing.
As the bearings wear out the pulley will move around causing the belt to come off. When you replace the tightener you should replace the belt as well.

Most likely need to replace you accessory drive belt. However, before you do that make sure the tensioner is bringing adequate pressure to bear on the belt. The squealing is probably the side of the belt slipping in the metal drive pulleys.

If the power comes on and off, in all probability it is not a mechanical failure. Seems like the belt that drives the steering pump is loose, and when extra power is required, such as in a tight turn, then it slips and stops providing power assistance. Poke the belt with a finger to see if it loose, and tighten it accordingly. These pumps do not require much power, and the belt does not require to be extremely tense. By trial and error, tighten it bit by bit until it stops slipping. Over tensioning will provoke a failure of the pump pulley. Also check if the pulley or belt have grease on them, because that will contribute to slipping.

once the belt become loose it slips and its friction surfaces become damaged .. even if its then tightened properly it may still slip .. an old damaged belt should be replaced and tensioned properly ... its common for older type belts to slip and make noise .. it is not as common in later cars since they often have automatic belt tension and improved belts .. any slipping is a sign of some other problem ... one frequently seen problem on some cars is a pulley that is spring loaded to keep the belt properly tightened .. the pivot on the pulley freezes up and no longer maintains proper tension .. those pulleys can sometimes be re lubed but often are hopelessly frozen and need replaced ... also other pulleys and the alternator bearings can start to make a squeaking noise when the sealed bearings lose there lube .. you can put a drop of oil on each bearing to see if one quiets the sound ..

Sounds like a loose belt.

There are a few things that can cause a belt to slip like that.

The belt could be not tightened all the way. If it uses a sepentine belt with a tensioner, the tensioner could be bad. If it is not a serpentine belt, then you will have multiple belts and the one that is making the noise can be loose. Use something to pry it tight and tighten down the bolts holding the component th belt goes to.

It can also be a bad pulley. Pulleys have bearings inside of them, at times the bearings will go out and make the pulley hard to turn. You can usually find this easily by taking the belt off and turning the pulley with your hand. If it is hard to turn or makes a grinding noise when turned...it is bad and needs to be replaced.

Old belts can also cause this along with a belt that is wet. There is a spray on Belt Dressing that helps get rid of noisy belts, but I consider that a bandaid to a bigger problem.

Do you know which belt is making this noise? Usually it's the power steering belt, and sometimes it's the alternator belt. The power steering belt will make noise turning the steering wheel when stationary, the alternator belt will slip as you quickly rev the engine by blipping the throttle. In either case tightening the belt to the specified tension will fix the problem.

does it go away as it warms up ? or does it stay that way check belt tension

You need to tighten the belt or replace it.

You shouldn't need to most of the time all you need is a 15mm wrench. Use it by turning the spring tightener inward toward the center of the motor than the belt should come off. Also when you take it off make sure you know how the belt goes around the pulleys so everything will work together like normal. when putting the belt on you should use the wrench to turn the tightener back inward and slip the belt back on and make sure it looks just like the old one when its on.

Check and tighten your drive belts / fan belts. The noise you are most likely hearing is the belt slipping on the alternator pulley. Its worse in the morning because the starter takes more out of the battery when the engine is cold. This in turn leaves the alternator with more load to replenish charge. More load = more resistance on the pulley to turn, hence the belt slips if too loose.
Cheers John