Changing a belt is a basic & routine maintenance
procedure. Maybe you can recruit a more mechanically inclined friend to walk you through the process?
What type of engine
do you have?
On almost all makes/models it is just a matter of loosening the bolts that hold alternator in position and swinging it toward the engine
so it applies (or would apply) the least amount of tension to the belt. The belt typically passes over three pulleys, but may vary by motor
: alternator, fresh water pump, main pulley (on crank shaft). Some raw water pumps are belt driven, some are not. With the alternator loose: put the new belt over two of the three and then walk it onto the third as you rotate the engine manually.
Its a good saftey practice to shut off the start battery
switch before working on an engine...you wouldn't want an acciddental start to happen with your hands on belt & pulleys.
I bet there is a You Tube video out there that shows this process.