Even tech wizards have a tough time with basic hardware installation sometimes. If you are in a position where you cannot seem to get your hp printer to accept a new ink cartridge DO NOT get frustrated or attempt to force the cartridge into place. Go, consult youtube for a Video on Toner or ink cartridge replacement.
Visually seeing the process take place before you, with warnings and helpful hints additionally, can clear up misunderstandings you may have because of the help manual (or if you lost the manual in the first place). It can also help point out steps where the printer may actually be broken, processes where you may need to watch again so you can figure out little ways to fix the issue without accidentally breaking the cartridge or the printer you only just invested in.
You can find these videos for just about any model printer and toner. The example above is specific to an ubiquitous line of hp personal printers. You can find them everywhere, especially in the possession of first time computer/printer owners who may not be comfortable with even basic maintenance of their new unit. These videos, with their paced, step by step guides and hints of important things to avoid, are perfect for this situation.
If, after using this video, you still have issues with your replacement, consider calling someone more experienced with technical issues or, if it appears that there is a major malfunction of the printer, calling tech support and possibly sending the unit in for repair or replacement from the manufacturer.