You should be able to log into your account on GoDaddy (I'm assuming you have access to it if it's your domain) and update the information. Google Apps usually asks what your provider is and if you specify GoDaddy it should give you instructions unique to them. the upload option is there if you don't have access to the domain, it'll let you simply upload or alter information of an HTML file on the site. Then it checks to make sure it can see your changes.
