i need help

[Trimoon]

where i find full black set what store i find that???

[h o n e y]

You can't find a full black set at any f2p store unless someone sells a set at a general store.
Rather than waiting for one to be sold, I'd recommend buying a set of full black armor off another player.
If you can enter the Champion's Guild (32 Quest points needed), Southwest of Varrock, you can buy a black full helm and platelegs if they're in stock there - it usually has 1 piece each, unless someone has bought it already.