Sprint iphone 5 invalid sim card?

I recently got an sprint iphone 5 and i've tried to activate it (I already have a number for it) but it says invalid sim card. Do I need to replace the sim or can i just take it to sprint and have them fix it?

Either the phone or the SIM needs to be fixed
take it to a sprint store, they can fix it for you.

Sprint is a CDMA operator, so there should be no SIM card involved and you should have the CDMA model of the iPhone 5. I recommend you speak to a Sprint representative either in store, online or over the phone. If it turns out that you have purchased a phone that is incompatible with Sprint's network, you could use a SIM from AT&T or T-Mobile. All iPhones purchased from Apple for use on the Verizon or Sprint networks can't use SIM cards and are already synced to your wireless contract upon delivery.

Sprints iphone 5, has a sim card slot but its inactive.
sprint doesn't use sim cards.

Sprint is a CDMA carrier. Don't use SIM cards. Sprint should know what to do to activate it.