Makes high pitch humming sound, chain and bar heats up. Saw doesnt' cut

The bar and chain are running without oil. Take the side cover off where the chain is driven from and remove the bar and chain. Use compressed air to blow all debris from the area. Start the engine and watch for oil coming out of a small port near the clutch assembly. If oil passes (good!), then clean ( at the drive end of the bar) the two smaller holes and their passages into the track which the chain runs in. They are likely to be filled with sawdust and other debris. Clean the entire chain track around the whole bar. Use engine oil in the two small holes at the bar tip to lubricate the sprocket bearing. Back off the chain adjuster screw somewhat and reassemble everything--put the bar on first and then work the chain on, then the side cover--work the bar fore and aft to allow the small tang of the adjuster to drop into it's hole at the bar rear. Make sure that the cutting side of the teeth are pointing toward the engine on the bar bottom. With the cover on and mounting nuts slightly loose, adjust the chain tightness so that the chain doesn't droop away from the bar bottom, but still allows the chain to be moved by hand--remember to lightly oil the chain first with engine oil. Tighten the bar mounting nut(s) and recheck the chain for droop. Make sure that you have bar oil in the tank, then start the engine and hold the bar tip near a piece of paper or cardboard. After running for a little while, the tip should throw off a very thin line of oil. Next, if you have a vise, put the bar center into the vise so that the chain is free to turn. At this point you need to file each tooth to sharpness at 30 degrees from perpendicular to the bar and 10 degrees below chain horizontal. Make sure you use the correct size file for your chain. Work your way through one side, then work the other side--be consistent with cutting angles during filing as uneven filing will result in the chain trying to cut at unintended angles.
If no oil came out of the engine when running the bar-off test, make sure there is ample oil in the tank, then you have either a plugged inlet filter in the tank, tubing kink/breakage, or a defective oil pump. You must be sure that oil is being pumped from the chain drive area before putting things together. Hope this helps!