You uploaded an APK that is not signed with the upload certificate

I’m trying to add my downloaded .apk file to the Google Play Console and getting this error:

“You uploaded an APK that is not signed with the upload certificate.” I generated an upload certificate in Android Studio after this happened but I’m not sure where to apply it. Do I do that in Thunkable somewhere? Do I do that on the Google Play Console?

I have a .jks file but when I try to import that into my Thunkable project as a keystore, it won’t let me (it’s greyed out in the Finder).