I found a iphone 5 with no sim card?

I was at the store found went into the fitting rooms & there it was and iphone 5 i took it home check its pocket thingy & it had no sim card in it? Can i use it?

Yeah you can use it if you don't have the sim card also. But you can't make phone calls. You have to have buy a microsim because an iPhone 5 uses microsim.

It will need a SIM card. And you will need to figure out which carrier it's under as well. AppleCare can help with that.

Since you stole it from the store, no, you can't use it, at least not legally. Bring it back to the store and maybe they can find the rightful owner.

That's cool and lucky you found it.
You can use it with your own SIM card (T-Mobile and AT&T in the US) but it may be usable only on one of the carriers (carrier locked). You would have to check a website see which carrier it is locked to be able to use it.

If I were you, I would give it to the target customer service or help desk. I'm saying this because someone is probably frantic losing their device and since there's no SIM card, it's most likely they bought the phone that day.

I'd take it back to the store.

Often store security or local police place "valuable" objects in dressing rooms to see who takes the bait. The phone is easily tracked once turned on. This is similar practice in the show "Bait Car".