How can I update image or do other maintanance in customer tenant's deployed from Marketplace?

Question

I am working on the application that will be deployed by customer to his subscription by using Azure Marketplace offer. It is deployed with ARM template. I have attached identity to the template. My question is how can I get into the customer subscritpion from my C# code application to manage this group for example to change image of some container app or tweak some settings inside the managed resource group.
Of course application is deplyed as a publisher managed app.