How to choose the texture of the armor, how to create a hammer, I hire teammates

Hello, when I want to choose a texture for my moded armor I can only mark: Select the texture and its does not open the files for me and I can neither drag them. As I make a mod for my minecraft server and I do not know how to code mods so I use MCreator and as I do not know all the functions I would like to know how to make a hammer which breaks 9X9 (the blocks) to mine more fast and its also i don't know how to do its (again sorry for english i use google translation) i would like someone to answer me urgently for the armor the hammer i will watch tutorials. cordially
 And I'm also looking for teammates