SiteGround already has a great guide for this process, but it assumes a bit of familiarity with their SiteTools dashboard. If you’d like a ‘whole-process’ guide, hopefully this page can provide that for you.
After logging in to your SiteGround account, click your initials in the top-right corner, and click Manage Users.
From the Users and Roles page, click the Add New User button
In the box that pops up, select Collaborator, then choose the website you want them to have access to, fill in their name and email address, and click Add.
You should see a Success message letting you know that SiteGround has invited that person to help with your SiteGround hosted website.
Adding a collaborator to multiple websites
If you have multiple websites, and want to invite one person to help with many of them, then after you complete the initial invitation, you can go back to the Manage Users page, click the dots next to the person you invited, and click Add Websites.
