I layer down some tracks but, they need sustain, is there anyway i can add sustain to these tracks?
What exactly are you asking? Is it a Midi file or is it analog audio? I would try going into the hyper editor. Also the help bar in logic is great. I would search there.
k, its a midi file
Open Piano roll (Type 'P' or click 'Piano Roll' at the bottom of the arrange window) and simply drag the right hand side of the notes for the sustain you need. You can also automate a sustain pedal effect for piano/keyboard-based instruments by hitting 'A' to open up automation and then selecting the relevant target parameter to automate.