To tweet, first you need to enable your mobile phone on Twitter.com, so do it now while you can. Go to your Twitter homepage, then to “Settings” and then “Mobile.” Insert your cellphone number under “Activate Twitter text messaging,” and then you’ll have to text “GO” to the number 40404.
Once you’ve done that, you should receive a text message telling you that your phone is now activated. You should also see new settings on the webpage that allow you to enable or disable text notifications.
Now, to tweet, just write a text and send it to 40404.
To use Facebook, log into Facebook.com and go to your “Account Settings,” which you can find under the arrow next to your name on the top bar. Then go to “Mobile,” introduce your number and click on “Activate Text Messaging.” You’ll have to select your country and your carrier. Once you’ve done that, follow the instructions on the screen and text the letter “F” to the number 32665.
Finally, you will receive a confirmation number on your phone. Insert that number on the page. You should then receive a text message that will confirm that your phone is activated.
Now, to update your status, you simply have to write it in a text and send it to 32665.
Source: Mashable