To enable MarkGit to communicate with GitHub, it is necessary to log in to GitHub if this has not already been done.
With MarkGit, click menu -> "Select a local repo", and navigate to the Obsidian Vault.
MarkGit might prompt "Do you want to initialize the folder as a git repo?", in that case, just click "OK" to confirm.

Open "https://github.com" with your favoriate web browser, and create a new repo.

With MarkGit, click the "i" icon at the top right, then click "Add remote"
Input the URL of the repo, then select GitHub credential.

With MarkGit, go to the "Sync" view (by clicking the 2nd icon at the bottom)
Then click the "Sync" button.

Once it is completed, we will be able to browse our contents in GitHub!

Open the iOS built-in "Shortcuts" app,
When every time, when we open Obsidian, MarkGit sync UI can be popup and sync data for us!