with the new update all you need to do is:
if there is an available world to join you go to the end of the list of your worlds and if there is, the name will be in blue. just tap on it and there you are, you've joined someone else's world. theres also REALMS but you need a minecraft account and its really hard to get onto a server anyway as there are so few.
hope this helps. :)
P.S: if you havent updated yet i think that you also need to have the SAME wifi