1. Check to insure the cover is shut down completely.
2. If the "Ink Drop" Icon is blinking you are either out of ink, or there is a problem with the cartridge carrier. So open the cover - the carriage should move to the middle, if not it is bound up somewhere. Check the guides and around the carriage area for gummy labels etc..
3. If the carriage moves to the middle, release the ink cartridges and replace.
4. If the "Arrow" Icon is blinking, this could be a result of a paper feed error. Remove the paper from the tray, open the cover and insure no jams are in the rollers. Shuffle the paper lightly and place back in tray. Check to make sure the tray is pushed completely forward and then press the "Arrow" Icon button until a sheet is fed into the printer.
* * Note: When you are replacing the Ink cartridges and before you remove the tape from the bottom heads, give them a shake to lossen up the ink before installing.
This link will take route you to HP's support and more troubleshooting techniques for your printer.
Hope this helps..