file->interpret footage- loop 5x or something or use loopout() expression described below.
layer>time>enable time remapping… then select the time remap property that pops up for that layer and enable expressions for it (animation>add expression) then type loopOut() in the expression field.
the clip will loop for the duration of the comp. if you adjust the length fo the comp, you may need to extend the length (out point) of the layer (as you would with any layer).(kevin)
more info:
https://forums.creativecow.net/thread/2/942061#942077