Unable to upload custom theme using the "Upload app"

[Audrey Guillemot]

We are planning to create our own theme for Confluence. We were trying to upload a sample CSS theme from the documentation. I’m running into an issue where I’m unable to upload a custom app. I followed the steps in the documentation here: https://confluence.atlassian.com/upm/installing-marketplace-apps-273875715.html. When I click on "Upload app" in the "Manage apps" page I only get an option to install "From this URL" (i.e. the Atlassian Marketplace). There’s no option to upload the file from my computer. Apps and Integrations are allowed on all versions of Confluence Cloud so I don’t think it has to do with our particular Cloud license: 

[Nic Brough -Adaptavist-]

You are reading docs for Server/DC Confluence.  You don't upload themes or apps to Cloud, you request them from the marketplace or give Confluence a url to set up the connection with.

For themes on Cloud, start at https://developer.atlassian.com/cloud/confluence/theme/ - the installation instructions (make it available on marketplace and pull it) are linked near the bottom.

[Matt Reiner _K15t_]

@Nic Brough -Adaptavist-'s answer is on point!

Not sure what you're looking to do with the theme, but my team is also about release Scroll Viewport for Cloud. Perhaps this is helpful as well.