Need Help With IPhone 6?

Today, I bought an IPhone 6 from a friend of mine. It did not have a SIM card and when I try to start it up it needs a SIM card. I tried almost every method such as logging in through ITunes and it still requires it. When I put my friends SIM card, it texted people from his phone number. I do not know how SIM cards work or where to buy them if I even can. Should I ask for my money back and save up for an IPod or something? Or is there a way to get a SIM card or just activate the phone without it. ( I don't think I can, I think the phone is locked). What do I do?

You will need a sim card or else just consider switching to ipod

If you want to use it as an iPod, then any SIM will do, even a deactivated one, as long as the SIM matches whichever network the phone is locked to or if the phone is unlocked to all networks.

Subject to the same locked/unlicked rules, getting a SIM is easy. Just buy any prepaid credit SIM or take out a monthly contract phone package (the provider will send you a SIM). You can also look online for a free SIM: many providers send them out at no cost. Most come with no prepaid credit of any kind and a few occasionally ate offered on deals which give a very small anount of free credit. You only need credit on the SIM (or a monthly contract) if you want to use the iPhone as a phone. If you just want to use it as an iPod then no credit is needed.