You register your MyHeritage DNA test at the GEDMatch.com website and then use only the GEDMatch ID you get to enter your DNA at WikiTree.
At WikiTree we do not analyze or store your RAW DNA. We help DNA cousins find each other. We do that by letting you identify which tests you have taken and whether you have uploaded your test to the GEDMatch.com website.
When you add your DNA test information, it takes about 24 hours for the system to add your profile link to the profiles of your ancestors and their descendants. That is why there need to be profiles for your ancestors.
Check out that How-To link we sent in your confirmation email, especially the Getting Started with DNA part at the bottom. Then start adding your family profiles.
Please make sure to review any suggested matches because there are lots of profiles already here. You may be able to make a fast connection to the Global WikiTree.