Github allows you set a custom domain for your Github pages sites. The first step is to configure a CNAME record with your DNS provider. The second, also the last step, is to create a CNAME file in the root of your Github pages directory.
##Setting up the DNS
If you are using Digital Ocean as your DNS provider, configuring a subdomain to point to your Github pages is easy. Login to your account, click on DNS and add select your domain. You then click on Add Record and choose CNAME as the record type.
##Updating the CNAME file You need to create a CNAME (uppercase, no extension) file in the root of your Github page directory. The easy way is to login to Tinypress, go to Settings and in the Custom Domain section, enter your new subdomain and update.
Or, you can go to the directory on Github and click the + icon beside the directory name to create a new file. You simply type the custom domain (e.g, blog.example.com. No http:// or https://).
Another way to do this via Prose. Login (via Github), go to the directory and create the CNAME file.
With those two steps done, correctly, your subdomain should point to your Github page in no time. Github says it may take up 24 hours though.