Official launcher: 
Install Fabric loader with their installer. 
Put the Fabric API & MineLP mod .jar's into the .minecraft/mods folder (create if it doesn't exist). 
Start the Official launcher and launch under the newly created profile. 
If you need help finding your game's folder see https://minecraft.fandom.com/wiki/.minecraft

MultiMC: 
Create an instance, Select 1.18.2. 
Right-click new instance, click edit instance. 
In the versions tab, click install Fabric. Once installed, go to the Loader mods tab. 
Drop the Fabric API & MineLP mod jars here.
If you need more help, use google