Hi @Anonymous ,
Do you want to connect with sharepoint?
Could you tell me whether do you want to connect with online sharepoint list or on-premise sharepoint list?
1)connect with online sharepoint list
Firstly, choose "cloud service".

Secondly, fill in the sharepoint site URL here:

You could find your sharepoint site URL in your site's home page.

The site URL should be like this:
https://....sharepoint.com/sites/test315
2)connect with on-premise sharepoint list
Based on your URL(...aspx), I think that should be a on-promises sharepoint list.
To connect with on-premise sharepoint list, you do not provide the site URL, you just need to provide account name and password.
Firstly, you need to use gateway to connect with on-promises data source and you could only use gateway in default environment.
Secondly, only premium license could use gateway.
After you install gateway and finish configured it, create your app in default environment, connect with sharepoint,choose "on-premises".

Choose gateway and fill in your sharepoint on-premises account name and password.
Please notice that powerapps only support SharePoint versions 2013 and 2016.
Both of these two situations need you have permission on the list that you want to connect with.
Best regards,