Office 365 and godaddy hosting

Since you say your domain is managed by Office 365 (i.e., Microsoft's DNS is the authoritative name server for your domain) then this is straightforward. I have this same setup myself.

1. In the Office admin center, select "Setup/Domains" from the left nav menu.
2. Select your domain from the list that gets displayed and a fly-in window will appear.

    

3. Click "New Custom Record" and create a new "A" record with a host name of "@" to point to the IP address of your web server. If you already have an "@" A record, edit it to point to your web server's IP.
4. Click "New Custom Record" and create a new CNAME record with host name of "www" that points to your domain name. (E.g., CNAME www mydomain.com)

One propagated, you'll be able to access your GoDaddy website via either "www.mydomainname.com" or "mydomainname.com".

Bob