How to activate my iphone 6 without the orignal carrier sim

Hi,

I bought an iphone6, it was working as an ipod.

However just to back my data on the phone, i have rested the phone. Now i cannot activate it, because i don't have original carriers sim.

My question is, If i get my IMEI unlocked, would i be able to activate the iphone with any other sim card??

Because what i have heard is that after the carrir unlocks the imei they send us a code or something, i don't see any option to put the code.

And i am not sure, if i pressed to setup as new or setup from backup option.