HOW TO USE THE UNLOCK CODE GIVEN BY THE TMOBILE TO UNLOCK THE IPHONE?

So ok. Here's my concern. My relative sent me an iphone from the US locked under tmobile and the contract was finished and paid already. All they gave me is an unlock code which i freakingly don't know how or where to put it. I tried to follow their instructions to "put the sim card… Etc.restart.etc.complete the set up process.etc." but there's no form or bar to put the code. T_T. Any one has an idea how to use the code?

Check the TMobile support page

Done. But based on the tmobile support page. They have the same instruction.