If you would like to be eligible for text messaging, click on your name in the top right of your screen, choose My Profile, then select Edit Your Profile. On the resulting page, scroll down and locate the fields labeled Mobile Number and Mobile Provider.
Fill in your phone number and choose your provider from the dropdown. Save your changes at the bottom of the page with the green button (the button may be labeled Finish or Continue).
The next step in this process is to ensure your account is enabled for text messaging. Go to your personal notifications page by clicking on your name in the top right of the screen then choose Settings (near the bottom of the list). Double check to ensure the setting labeled Allow organizations to send me text (SMS) messages is toggled on (or green).
Tip: If you'd like to hide your phone number but remain eligible for text messaging, navigate to the Privacy Settings tab on the left-hand menu. Click the checkbox next to your phone number and save. This will remove your phone number on your public profile.