Twitter Feed integration not working

We were trying out the Twitter Feed widget.

Unfortunately the integration is not working and no tweets are popping up no matter what username / consumer key / consumer secret / access token / access token secret
were inserting. The row is remaining grey.

We were also checking the video https://www.youtube.com/watch?v=5oYIDDm6wZc
Also from this video it is not clear what the right keys are or how (is e. g. the bearer token needed yes/no?) and if an app has to be created and if yes, how.
It would be great to have some guidance so that we are able to use this widget at all.
Many thanks in advance!