Here's how to share a site within SharePoint:
Navigate to https://www.office.com/
On the left side of the screen click on the green SharePoint icon.
Select the SharePoint you would like to share.
Once on the SharePoint site, Click the “Documents” tab.
In the top right corner click the “Share” button:
In the dialogue box, input the user name of the person you would like to share the file with.
Once a name is found and selected, you can choose to grant the recipient read only, ownership, or editing rights from the drop-down arrow. Once a role is selected, press Share and they will be granted permissions. (The person will receive an email confirming the sharing, and you will be copied on it).
SharePoint