I had been frustrated at not finding instructions for using Twitter. Somhow today I looked in Help and discovered that's where all the information is.
So today I tried to add my phone number to see if I could text message a tweet and it worked fine after adding my phone number under Setting>Devices.
I must admit though that if my daughter hadn't helped, I would have still been frustrated because in trying to add my phone number I had to verify a letter code. I mistakenly thought that I had to verify by phoning 40404, but I actually had to send a text message to 40404. Aren't families great. :-)