For information on "how to's" regarding basic functions of Studio One, your best bet is always going to be your reference manual.
By opening the manual (in the Help menu of Studio One) and doing a search for "looping" you'll find the exact information you're looking for.
The screenshot below was taken directly from the section labeled "Mixing > Looping During Mixing":
Regarding your question about duplicating tracks, again this is something spelled out exhaustively in your manual. There are a number of ways to duplicate tracks. Please see your reference manual under the section "Arranging > Duplicating Tracks":