How can i enter yellow spire do i need somekind of special item?

Try wearing the entire uniform you made through the main quest previously through going to the character tab and costumes then attempt to enter the dungeon.

Tried that didnt work D:

Can you post a screen shot of what your problem looks like? Because the only thing I can think of at the moment is that you aren't wearing every part of the guardsman uniform.

oooooh im sorry i didnt notice i had a new uniform.. Thank you sorry for me being so noob :3