Ok, there's some info in the godot doc. I am not sure where your progress actually stops or where the problems begin. It seems you've already generated an release/upload key and don't know how to proceed?
You already created a debug key? Then creating the release/upload key is very similar.
Usually you use two keys. I'll just roughly tell which one is for what.
The debug key is used for local tests and you you can install apks signed with a debug key on (roughly) any android device when it's configured to allow the install of "untrusted" apps.
"Untrusted" because the debug key (as well as the upload/release key) are both so called "self-signed" certificates. This means that you create the keys just on yourself and there's no trusted party that acknowledges that these keys/certificates are from your very person.
Then there's the release key. That is actually very similar to the debug key because you create this key also yourself. But in another keystore.
So in the godot docs is mentioned the basic command line which you use to create the release/upload key:
Uploading an APK to Google’s Play Store requires you to sign using a non-debug keystore file; such file can be generated like this:
keytool -v -genkey -v -keystore mygame.keystore -alias mygame -keyalg RSA -validity 10000
This keystore and key are used to verify your developer identity, remember the password and keep it in a safe place!
This keystore/key is used to sign the app before you upload it to the google play store. Usually, it is just used for upload. Google will sign that app later (automatically) with its own "trusted" key.
So, you created your own release key with the command line mentioned above (replace "mygame" with the title of your own game to be later able to identify what that key is for.)
Then you enter the key data in the "release" key section of the godot android export dialogue. Just as you did previously with the debug key data.
Then export the apk (uncheck the export with debug information).
Until here it is all detailed in the godot docs:
The next step would be to upload the app to google play.
If you let Google handle the signing then google play will learn your upload key the first time when you upload the app to Google Play.
Here's the section in the google docs about it:
2. Sign in to your Play Console.
3. Follow the steps to prepare & roll out your release to create a new release.
4. After you choose a release track, configure app signing under the Let Google create and manage my app signing key section as follows:
* To have Google Play generate an app signing key for you and use it to sign your app, select Continue. The key you use to sign your first release becomes your upload key, and you should use it to sign future releases.
Creating and using the "release" key is very similar to creating the debug key. You create both on your computer.
The "release"-key is basically just used to sign the app before uploading it to Google Play. It is only used between you and Google Play. Therefore it could also be called upload-key.
If you run into any problems in the play store then first make sure that you completed all mandatory sections of your game listing. I read often of people that though that a warning message (after upload) stopped the release of their app but then they noticed that they forgot to fill/complete other required data in the store listing (like Content Rating, GDPR / Data Privacy, etc...).