Problem on installing extensions

My computer downloads the extension normally, but when I click on it, it shows the message “this file does not have an app associated with it for performing this action. Please install an app or, if one is already installed, create an association in the Default Apps Settings page.” But I already have the Sketchup 2017 app installed and I don’t know what to do. Can someone please help me?

Clicking or double clicking on an extension is not the right way to install it. Instead go to Window> Preferences>Extension Manager and click on Install Extension. Navigate to where you saved it and open it.

Please fix your profile. You have entered “2017” for operating system and graphics card. Neither of these are correct.