On my 90 legacy there is no ac. how hard is it to a one? Ive seen pick a part ones on ebay for about 60. New for 200 ish? But I will need the hoses as well. Any info on how to add one anywhere? Thanks

Taking a picture of your engine bay may help.  particularly the area around the drivers side front corner. 

Did it originally have AC or not?

Does it have buttons and controls for it inside or a condenser in front of the radiator?

If it used to have it then yes just add all the necessary parts that are missing which is usually just the compressor, two compressor hoses, bracket, belt pulley and bracket. 
 

if it didn’t originally come with it you won’t be able to do it unless you want to put way more work into it than what it’s worth. 
 

you’ll have to add all the parts which is extensive - Compressor bracket pulley hoses condenser firewAll hoses drier Sensors evaporator, pull the entire dash or find a work around....that’s days and days of work and then you can’t turn it in and off - are you going to hard wire it or swap wiring harnesses...that’s just a mess of a job to do much less explain easily.