If you haven't downloaded the rig, you can get it on Gumroad. The rig is available for free. But you can get the optional Extra Content that includes additional presets, additional modules, and more.
To download the rig for free, select the Base Content option, fill in the price column with $0, and select the I want this! button.
Select Base Content and fill in the price with $0
After that, you'll be asked for your email address. Just fill it up and select the Get button.
Fill the email address then select the Get button
Once you've done that, you'll be greeted with this page. This is where you download the rig. Note that there might be several versions available. The Latest version folder contains all the MCS versions of the rig, while the Legacy version folder contains all the previous versions of the rig (R1, R2, and Remastered).
It is recommended that you download the latest version available. Using older versions is fine, but you might encounter issues. And rig support is only available for the latest version.
Download page where you download the rig
Guides
Here are some guides to get started on how to use the rig as quickly as possible:
You need a basic knowledge of Blender 5.0 or above to use this rig. If you're a beginner, I recommend learning the fundamentals first before getting started.