There are basically tow ways to do this. The first, the most basic, is to add your 'icon' layer to the time line, size and position it, set an in and out point, animate the opacity of you don't what the icon to pop on and off, then duplicate the layer, move it and adjust the in and out point, then do it again.
The second would be to use a particle system like Trapcode Particular, set up a custom particle using your icon and then adjust the emitter, birth rate, size, number of particles, physics and other properties to make your icon's pop on and off the screen. Depending on the design and the numbers you need this may be the easiest approach.
If you haven't purchased Trapcode Particular, there are several particle effects that come with After Effects including CC Particle World, Particle Playground, Foam, and others.