Is there any song that you like very much? Perhaps your favorit idol? Download the song's tab (just google.com and search for "XXXXXX tab"). That's the best way if you ask me, cause after a while (days or maybe weeks) you will find yourself playing sections of the song or even the whole song.. Once you are there, found a bassplayer who also like the song and before you know it; You got a band!

Good luck

Ps. If you're not sure of which song you like, let me suggest Led Zeppelins "Stairway to heaven" or Metallicas "Nothing else matters"! They both have really easy-played intros and correct tabs are all over the net! Ds.