How to Play Subsets
What are Subsets?
Subsets are supplemental achievement sets for a game that contain achievements which may not be a good fit into the main (core) set. There are many types of subsets. Subsets typically require an extra patch or sometimes an alternate revision/version of the game.
Getting Started
When the subset you want to play requires a patch, follow these steps. These steps can be followed for patching a ROM to play a hack.
Step 1: Download the patch for the subset of your choice. We'll use this subset as an example (in this case, Super Mario Land [Subset - Bonus]). Patches are hosted on RAPatches.
Step 2: Go to ROM Patcher JS, a free online tool to patch your ROM.
Step 3: Choose your ROM in the upper field and your patch file in the lower one. Make sure that you are using the correct ROM for the patch (see the readme file that usually comes included with the patch itself). Checking the CRC32, MD5 and SHA-1 hashes between both fields also helps (in this case, the subset offers patches for both the original, unmodified Super Mario Land and the Super Mario Land DX hack. In this tutorial, we'll use the one for the unmodified game). Rom Patcher JS will also tell you the required CRC32 hash for the patch to work.
Step 4: Click/tap on "Apply patch" and download your patched ROM.
Step 5: Open your emulator of choice, then load your patched ROM, and see if a pop-up appears telling you that you're using "X Game [Subset - X]". If so, congratulations! You have properly patched your ROM! Otherwise, repeat all the previous steps.
For a full list of subsets you can try, check out this hub.