if you dont know how rival rebels work, here is the website:
if you dont know how flans work just look in your controls than you will see wich buttons you will need.
Type in the modpack name (BOOM PACK by ADI_POWER) or paste the following url into the search box.
Finally, click Install at the bottom right of the launcher after you select BOOM PACK by ADI_POWER from the list on the left. The launcher will handle everything else!