If you mean animated as in moving, than you need some skill in that. you should practise simple things or use tutorials. You should use Adobe Flash, or I thnk there is a Gimp animated thing you can use. You can use a mouse, but it is easier with a Wacom Tablet. You need to know how to use Flash and the Gimp animation program, so you can use tutorials.

If you mean animated as in renders, you should use Photoshop or Gimp. You also need practise, and if you have one, a Wacom Tablet. A mouse can be used, but it is easier with a tablet (I don't own one, and it is easy with a mouse). You need to know how to use Photoshop and Gimp, so you can use tutorials for that.

After you know what you are doing, both are really easy!
Hope I helped!

animated pictures or renders? animated pics are moving whereas renders are edited screencaps