@TheWolfieQueen If I'm right it is just as simple this:
1. Make sure you have optifine installed for the version you want to play Minecraft on
https://optifine.net/downloads
2. go to the website you want the shaders of and download them, in your case:
https://bitslablab.com/
3. The downloaded file should look like "BSL_v7.1.04.1.zip" the .zip might not show if you don't have file extensions enabled.
3. Copy or Move that file you download to %appdata%/.minecraft/shaders
5. Restart your Minecraft.
6. Open the version with optifine installed.
7. Go to Settings > Video settings > Shaders. And click on BSL_v7.1.04.1.
8. You should have shaders enabled now
If this does not work please reply so I can try to help. But I think this should do the trick.