how the hell
 

how in the hell do you add legatos on this program i tried to add one but it just beeped at me and did nothing.

You don't. But there's no real need for them.

You can however notate unpicked slides between notes, and you can tie two equal pitched notes together.

if you dont have a good sound card that could be another problem

the most you can do is make them all hammer-ons and pull-offs. they'll still sound like they're all picked though

I don't think the program makes a different sound for hammer ons and pull offs, I think the only difference is what you see on your screen. But what G_urr_A said works: the slide doesn't give an attack to the note you land on. The only problem with slides is that it gives you a perfectly gradual raise (or lowering) of the note that is played so it sounds exactly like a bend! (or release)
It's like it's programmed for fretless instruments ....

put the cursor to the starting note and press "l" to the note you want the legato slide to go to...