Step 1: On your organisation page. Click on the repositories tab

Step 2: Click on any repository you want to share. On the repo you selected, you can see a settings tab. Click that tab.

Step 3: On the settings page, you’ll see a left sidebar menu. Click on the Collaborators

Step 4: On the Collaborators page, click the green button (Add people) under the manage access container.

Step 5: Type in the email address of the person or organization you want to share the repo access with

Step 6: Check if the invite has been sent