Using it is pretty simple. Enter your base stats and gear into the appropriate spots on the Main page. Other is a column for any other source of INT/MAB (atma, buffs, etc.) For elemental potency, you simply enter how much of it you have through merits or atma (So Atma of the Beyond only would yield a value of 30 potency.) Attack merits are the 'potency' merits you have for that element, enter how many of them that you have. For NQ/HQ staffs, enter a 1 if you're using them (if you enter a 1 for both it will use HQ.) For day/weather/tonban/zodiac/twilight, enter 1 if you have that item (2 for weather if it's double weather.) You can also enter monster stats into the part below the INT/MAB section. MDT is expressed in n/1024, so enter 512 for a 50% MDT reduction.
There is also another part for INT/MAB just below the total, it's labeled Versus. This is tied to the +INT and +MAB sections and the earth/water/wind/fire/ice/thunder pages. Basically this is what I made the spreadsheet for. If you're a bit confused over which piece of gear to use (Searing Sash vs 7 INT waist, for example), you can simply leave the waist INT and MAB zero and then enter 7 INT and 3 MAB into the versus section. You can then either look at which is higher using some arbitrary mob INT value, or you can go to the earth/water/etc. pages to see which will produce better results for mobs of INT values equal to and between 1 and 150. The pages have a graph that displays the difference between the expected damage using the versus INT and the versus MAB. So if the value for some spell is greater than zero for a mob INT range, that means that the versus INT produced better results. If it's negative, the MAB would be a better choice.