Ok, the easiest way that I have found from my PC, is to install iBrickr. Once you install this, you can then do 1 of 2 things:
1: If you havnt already installed NES, install it using iBrickr. Once this is done and iBrickr notices you have installed NES, you will get a new link for installing ROMS. Click on that link, navigate to your ROMS, select a ROM and upload it. Very easy, but you have to install NES with iBrickr to work.
2: If you installed NES through anything besides iBrickr, you have to navigate to the folder they are located. Open up iBrickr, select the files link, then navigate to /var/root/media/ROMs/NES/. Once you have navigated to this point, Select the upload files button, navigate to your ROMs, select a ROM and upload it.