Lesson 8: Change your nameservers to point to your hosting location
Lesson 8 Chapter 4 Module 1
NOTE: VIDEO UPDATED DECEMBER 2019
A quick pictorial walk-through:
Simply go to your account and click on the "DASHBOARD" link (#1). Here you should find a "MANAGE" link button for your domain (#2). If you don't see the "manage" button, click the "Domain List" link in the left menu to bring up the list of domains you own.

On the next screen go to the "NAMESERVERS" section, and select "Custom DNS" (#3):

In this section, copy the two Nameservers from your SiteGround account, as shown in the video above. Save your changes, and you're all set.