How do I share iCloud with my family after I already upgraded to apple one and I already had the family sharing

See the instructions in Share an iCloud storage plan with your family - Apple Support including the following:

If you already use Family Sharing, you can set up shared storage for your existing family members from your device Settings or System Preferences.

On your iPhone, iPad, or iPod touch

1. Go to Settings > [your name].
2. Tap Family Sharing.
3. Tap iCloud Storage.
4. Follow the steps to share your existing plan, or if necessary, upgrade to a 200GB or 2TB plan.
5. Use Messages to let any family members with an existing paid storage plan know that they can now switch to your shared storage plan.