Your Manifold Creator contract allows you to add and remove administrators to your contract. Administrators are wallets that have permission to interact with your contract and do things such as minting tokens, setting royalties and registering extensions.
To add administrators head over to the settings of your contract in Manifold Studio and add the addresses of the administrators you want to add to the "Approve Admin" section.
To remove an administrator, simply follow the same steps on the "Revoke Admin" section.

Where to see the admins for a contract?

Currently, Manifold Studio won't show you the admins for your contract. To see them, simply go to your Manifold Creator contract on Etherscan by clicking on your contract address inside Manifold Studio:
On Etherscan, click on the Contract tab
Next, click on the "Read as Proxy" tab
Finally clikc on the "getAdmins" function. There you will see a list of all the addresses who are an admin on your contract.