Restore icons to dock

Launch the program you want to appear on your dock. It should have a dock icon that appears on the far right of all your others, but to the left of the "line" where the trash can resides.

After the app loads, click and hold while pointing at the icon, you should be able to drag it to the left and the existing dock icons will make space for it. Put the icon where you want it, release the mouse button and close the program (command-Q). Your icon should still appear in the dock.

That's how I do it.

 

I believe that you may also be able to right click(Control- Click) on the app that you want to stay in the dock while it is open and select "Keep in Dock".
I'll check my mac to make sure but I'm almost positive that you can do that.

EDIT: Yes you can do that it should be the first thing on the menu when you right click