@loanet
The option should be on the Social Networking menu on the computer. It is "Update Social Media Status". On the phone it is on the Social menu and worded the same.
Is the option not there at all or is it greyed out?
Also, if you have used the computer security options to lock the computer for one particular sim, that will keep a lot of things hidden for other sims until you unlock the computer.
It's been a while since I played that career but if I remember correctly, you can't do it twice in a row. I think there may be a cooldown and you need to wait awhile before doing it the second time. Might be wrong on that though.
Hope this helps.
Edit: I don't remember which Charisma level gives you the option. You may just have to level up Charisma to get the option.