First, export out from your source as managed/unmanaged as to your preference.
Note: Ensure all environment variables are cleared out first of current values, as they are a pain to deal with in DataVerse for teams. I deal with this by using a manual Flow to update the value(s). See TBD.
Then, add the PowerApps (best to pin to sidebar) to the appropriate Team in Teams. This will create an environment which cannot be seen in make.powerapps.com, but can in emea.flow.microsoft.com. So go to flow and you should see the environment there with the base install of Contextual Help and the CDS Default Solution.
The MS doc page which is roughly up to date.
After importing, the app needs to be connected to Teams. Go into the appropriate team in Teams, and click the Power Apps button. Go into the Build tab, and there should be a Import Your Solution link; click that and import your solution file.
After importing, connect any connections required on import. Ensure all Flows etc are turned on. Bring in any data required using the MS Configuration Migration Tool. This can be done in Teams or in flow.microsoft.com.
Back in Teams, go into the team, clink on the Power Apps icon, and go to the Build tab. Go to installed apps, and expand out the app by clicking See all. In the solution, go to Apps and select the radio box next tot he app, and then choose Add to teams in the command bar.
In the advanced settings of the Add to Teams fly out, click Add to Teams, and hey presto, it is now added.
And as to Updating the Solution ..
When the bugs come in, and a new solution is created… Export your new solution from dev, and then go to https://emea.flow.microsoft.com/ and Import.
Note here there is no option to overwrite customizations as there is in a normal PowerApps import. This means if there are any unmanaged layers over the managed layer, then the import will report successful but will not update any of those components. Unmanaged layers are much kore common over Flows, especially with those pesky environment variables sometimes not updating (Try turning Flows off and on).