How do I make the enemies grow larger over time?

Total noob. I just finished the "Ghost Shooter" tutorial, and am trying to add new things to the game. I'd like to see how to get the "ghosts" to slowly increase in size the longer they remain on the screen, and I cannot figure this out. Help? Also, as mentioned, I am new, and know almost nothing about programming.

Thank you! I'm happy that I at least had the basic formula correct, although I didn't which function to use. Thank you so much!

igortyhon if you have the time, would you mind explaining why I need to use the "set Width to self.width*1.01"? When I was trying to figure this out, I was using the "scale" function, and it was not working out. Would you be able to explain why scale did not work, but your method does? Thank you again for your time and help.

-I'm going through all the monsters every second and increasing their width and length by 1% (it's just math)

-If you want to ask what's not working for you, it's better to show this place in a screenshot.