First off ...Welcome !
The Belt is loosed by the tensioning device...Read Carfully ..You must loosen the adjuster nut just out of site located just Below the power steering pulley.If you get in that vacinity with a flashlight you will see it. If I remember correctly it is a 16mm. You only need to loosen it a few turns, It doesn't need to come out. Then you can loosen the adjuster nut up top. Its the brass looking hollow 13mm next to the water pump. Be gentle with it they tend to strip.. and if it does it can be a nightmare. once loose you should have more than enough slack to remove the alternator.
Are you sure the alternator is the problem and not the voltage regulator? The VR is bolted to the Alt. and is a 20$ part much easier fix and well worth trying before the alt. install.
1957 Dodge D100
1967 VW Microbus 21 Window
2004 Beach cruiser bicycle
"It cannot be emphasized too strongly or too often that this great nation was founded not by religionists, but by Christians; not on religion, but on the Gospel of Jesus Christ. For that reason alone, people of other faiths have been afforded freedom of worship here." Patrick Henry 1776