PQ for Strava

I have the data to make two text files containing the required information.

But where exactly do the two files "client_id" and "client_secret" get saved or posted?

where is the 'root of your solution'?

//
// Make sure you have two files called client_id and client_secret in the root of your solution.
// signin to Strava and navigate to https://www.strava.com/settings/api
// Follow the steps and obtain your client_id and client_secret.
//

client_id = Text.FromBinary(Extension.Contents("client_id"));
client_secret = Text.FromBinary(Extension.Contents("client_secret"));
redirect_uri = "https://oauth.powerbi.com/views/oauthredirect.html";