It’s only possible to manage sites that are built with WordPress from the WordPress mobile app. You won’t be able to manage your site here if it was built using Wix, Blogger (Blogspot), SquareSpace, etc.
If you’d like to transfer your site to WordPress.com, so that you can use it with the app, we have some guidance here:
https://transferto.wordpress.com
If you have any further questions feel free to contact our Support team.