When you first log into Challengermode, one or more menu items will be highlighted in the left sidebar navigation.
Click on "Connect Summoner" to add a game account for League of Legends.
Add a LoL Summoner
Type in your Summoner (the name of the LoL game account) and choose the region. Europe West (EUW) and Europe North & East (EUNE) are currently supported.
Once your summoner is found you can choose to verify it manually if you want to play in the daily ladder right away.
If not, you can add your Summoner anyway. (Your summoner will be verified automatically if you play a tournament or a challenge using a Tournament Code.)