How to use apple id on iPhone 4 7.1.2 (11D257)

Hello!

Today i bought iPhone 4 7.1.2 (11D257) and i have a problem with login to apple id.

I have my old apple id and i remember password, but i dont understend where i have to write short 6 number code. What i tryed step by step:

1. Wrote my apple id login
2. Wrote my apple id password
3. Got 6 number code
4. Deleted my apple id password, wrote it again plus 6 number code

After this manipulation i coudn't login to my apple id

Please help me.

P.S. I know iPhone 4 is too old device, but i like it