Hi RedColes,
Thank you for contacting Apple Support Communities. Based on what you stated, it seems like you want to sign in with your Apple ID in iTunes on your PC. I would recommend you read these articles, you can access your music library as long as you're signed in with your Apple ID and iCloud Music Library is turned on.
If you don't have iTunes on your computer, get the latest version of iTunes. Then follow these steps to sign in:
- Open iTunes.
- From the menu bar at the top of your computer screen or at the top of the iTunes window, choose Account > Sign In.

- Enter the Apple ID and password that you use with the iTunes Store. Then press the Return or Enter key on your keyboard or click Sign In.
- Click iTunes Store.
Sign in to the iTunes Store on your iPhone, iPad, iPod touch, Mac, PC, or Apple TV
- Mac: From the menu bar at the top of your computer screen, choose iTunes > Preferences.

Windows: From the menu bar at the top of the iTunes window, choose Edit > Preferences.
- Select iCloud Music Library to turn it on.

- Click OK.
Turn on iCloud Music Library
Cheers.