To enable it, save this links as .ymp file.
After you download it, double click to install.
Next to continue. Then next to continue install:
Warning pop up, just click yes, if you sure to use tumbleweed repository:
Import Untrusted GnuPG key, just click Trust:
Then the installation will begin, (Internet connection must be active):
When finished just click finish:
Then open yast, -> install & remove software -> repositories, if you want to full rolling release then disable openSUSE 12.x version. Then OK.
To upgrade it, use command below.
If you still didn't disable other repo
#zypper dup --from tumbleweed
Enjoy rolling release. :D