How can I add mods in Fabric?
Because Fabric doesn't have a "Mods" button in Minecraft like Forge.
As with Forge, the mods must be added to the Mods folder. If you want to have the Mods button on Fabric you need the Mod Menu Mod.
And how can I add it once I've installed it?
You just have to put the mods in the mods folder and then start Minecraft.
I mean how can I add the mod menu mod?
Just like that
And where is this mod folder? 😅 (Sorry for annoying you, really have no idea about it…)
You can create it yourself. Make sure it is called "mods". Asking is not forbidden. I'm glad to help.