if you wanna to test you new made icon just make a new folder (any name) at....

usr/share/icon.....

put all your new icon in the new created folder....need to remember not all icon is at 64x64...most of them are at 48x48 so make all folder with different sizes & puts your icon in the proper folder....d4rk icon is your best example to see how many folder & icon needed to be created....
once you have put it all the use themes customizer to change your icon for testing....

for me the best example for adding new icon is on usr/share/icon/hicolor cause all icon are automaticly placed here after installing apps...you need to remember where the original icon is (folder & name) then put you new icon in the same folder in your new icon folder...do not replaced the hicolor icon cause if you do (without backup) then the icon will be permanently be replaced...