Super Admin Permissions not granted to Single Type within plugin

Hi, me again with another plugin-related issue.

I’ve added a singleType collection to my plugin and when I visit it in the Content Manager section I get a 403 error with a pop up “Information: You are not allowed to see this document”. Under Settings → Administration Panel → Super Admin I can see the permissions for Create, Read and Update are not granted. It is not possible to grant the permissions here so I suppose the question is two-fold.

Why are they not granted initially? And how do I grant them in code?

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