Now that your RAM ports are empty, open your new RAM sticks, and be sure to discharge static electricity again (just to be safe!). Insert each stick of RAM into its own slot, and press firmly until you hear a snap. This indicates the RAM is snugly in place. Push the clips in on the sides to be sure that the RAM stays in place.
If you have four slots and are upgrading two sticks, place the two sticks that were already in your computer in the two lower slots.