i need help installing a fanbelt on volvo 240DL

Earlier volvos had a split crank sheave. Remove bolts, places existing spaces before / aft of flange to tighten new belt, and you're done.

Later >anyone know how to install a fan belt on this car?

Or loosen alternator brackets and move it out of the way, swap belts, and retension alternator.

It's a conventional replacment, except for the fan shroud. You loosen the alternator to slacken off the belt, slip the belt off the pulleys and then you have to feed the the belt over the fan blades and out of the shroud. Take it one blade at a time, find the slight "loose" spot in the shroud and feed the belt through there, turning the fan as you go. Replacement,as they say in all the best workshop manuals, is the reverse procedure!