Instructions
Click on your Sim and click the "Neighborhood" icon located in the lower left-hand corner of the screen.
Select then click on the shop where you want to hold your autograph session.
Click on "Hold Autograph Session." Your Sim will automatically travel to the location once it is selected.
Select then click on any interested Sim that approaches you. Sims interested in an autograph will have a bubble of your face over their head, with a bubble of a book and a pen underneath it.
Click on "Sign Autograph." Your Sim will autograph the other Sim's picture, earning you 100 Simoleons for each autograph signed.