GoDaddy

https://www.godaddy.com/help/forwarding-your-domain-name-12123

Forwarding:
1. Login to Godaddy
2. Next to Domains click Launch
3. Choose connect to website. If already connected choose Settings -> Connect to website
4. Paste your flex link in the Somewhere else box

Masking:
1. In the Domain Manager, click on Manage Connection
2. Choose Update Forwarding
3. Choose Redirect typr of Permanent (301)
4. Under Forward Settings choose Forward with Masking
5. Fill in your Title, Description, and Keywords