Go to https://www.strava.com/settings/api and register an application. Only need to fill in a name and callback domain. For name pick whatever, for callback domain pick localhost.
After registering, you will see a table with one of the rows stating "Your Access Token". Click on the show link to the right of it to see it. This token is needed to access your data, so this is what you have to add to the configuration of this application.