You can set up two user names but it is tedious to do on one device with only one version of the word chums. You can go to settings and logout and then login in as a new user. You will need a different email. You then have to logout/login everytime to switch accounts.
We do have people who play with 2 accounts on the same device by having both the free and the paid version of the app. Different accounts can be logged in to each Word Chums and Word Chums free. However notifications can be inconsistent doing this.