How do you chande surp belt on pulley end of crank shaft

SOURCE: crank shaft doesnt line up with anyother pulleys

It may be a thrust bearing failure on the crankshaft. See if you can pry or push/pull the crank pulley in and out. If you can move the pulley in and out very much at all there is a problem with the thrust bearings and the engine will need major repair.

SOURCE: My brother and I discovered

If the pulley wheel doesn't seem to connect to anything else it is probably just your tension pulley.
These are only to keep the serpentine belt tight while allowing it to adjust to some limited extent.

You can replace the pulley itself. These commonly grind when they go bad, or in your case it sounds like yours just broke off..

SOURCE: The Serpentine belt keeps walking off the Crank

Before you change anything,,check and see if everything is in line..Also feel all the pulleys and make sure everything turns ok...If the powersteering pump has been replaced,,sometimes the pulley was not pressed on far enough..If it seem to be the harmonic balancer make sure its not damage and the bolt in the middle is tight...If you remove it..You remove middle bolt,,then you have to use a puller to remove the harmonic balancer itself..unusuall for the harmonic balancer to be bad unless it was hit by something