The instructions tell me to lift the lid, but I don't know how, it seems to be locked, is there something underneath I need to push or pull. I need to change the ink cartidges
On this particular printer there is no locking mechanism to access the ink cartridges. In order to open the cover, use a single open hand and place your fingers just underneath the screen on the front, and pull upward. The entire scanner piece should raise and a plastic bar on the right-hand side will lower down to prop it open.
If you're having a lot of trouble opening it, you may want to check around the sides of the printer to see if there is any tape leftover from when the printer was packed in its original box. When they ship a printer it is always covered in tape to make sure that nothing falls open or breaks before it's delivered, and there may be a piece of clear (almost invisible!) tape left over preventing the printer from opening.
Once it's open, the ink cartridges should come to the middle. Press down on the small lever on the print head (the ink cartridge holder) to pop the cover open so that you can install the cartridge.
Hope this is helpful!