Well its all very simple, everything you need is on one screen. Select the cart that represents the generation of console your games are for, then an import box will appear allowing you navigate to those ROMs (specific to the console only!) and once you import them Cachet does the rest!
Now it could be that you want to tinker a bit and check out the preferences:
I. Affix a region symbol to segregate games: that is if you have games from the Europe or Japan or the USA they are different, and so affixing e.g. a (E) for Europe onto the file name will let you know which is which
II. Affix the console type to the file name: this is particularly useful for series of games like Mario and MegaMan where the names are similar, but console dependet, and so a [SNES] will be added to SNES games and the like...
III. Back-up: this is on by default sp Cachet will make a copy of the games you submit to it before it proofs them, just in case. This replica will be deposited into a folder called Backup in the same folder that was imported from.
IV. Add/Update DAT file: from time to time the DAT files update, you will be presented with a copy upon download but they're probably going to be out of date by that time, so check ...www... for an updated DAT and import it. I wanted this to be automatic, but they don't have that service :((