itch.io

1. Download MultiMC
2. Log into your account there
3. Pick the version of Minecraft that matches the version of the mod you want
4. Download the inflation mod, and geckolib from the internet
5. Select your Minecraft install inside MultiMC and click Edit Instance
6. In there, click the version tab and then click Install Forge, then install the one with the star
7. Go to the Loader Mods tab, click Add, then add the mods you've downloaded
8. Go back to the main MultiMC screen and Launch

I think I remembered everything...? I have no experience with any other launchers, including the official MC one, so I can't help with those. The cool part about MultiMC is that if you want a SFW install and an inflation install, you can keep them separate, or if you want to have one install be the OG Minecraft, while having the other install be fully-updated.