How to share a SharePoint site
1. Navigate to the given SharePoint site you wish to share
2. Click the Gear icon in the upper right next to your picture
3. Choose Site Permissions
4. From there you can click Share Site, enter the email address of who you wish to share the site with, and hit add (You can also check or uncheck the send email box depending on if you want them to receive an email letting them know they have been added to the site)
5. After clicking site permissions you may get another menu depending on which type of site it is. Click on add members from here you can either add members to the group or you can share the site.
Click on Share site only and type in the email address of who you wish to share with, after that you can click the drop down next to edit under their name to change the level of permissions they have. Once that is set hit add.