How Do I Change My Ink Cartridge In My HP Photosmart C3180 All In One?

I am not familiar with the HP C3180, but I have other photosmart models. Make sure that the unit is powered (plugged in), turn it on, on front panel, the cartridge carrier should move into the center position allowing you to access the ink cartridges. Every HP that I have ever owned has had the ink cartridge diagram on the inside of the access panel.

Yes, the above is correct, however - if you cannot figure it out or have the little label missing on it. There are two slots, one with a green triangle and another with 2 different shapes. The left one is for colour and the right for black ink.
First you want to pull the desired cartridge out by putting a finger on both top and bottom and it should literally slide out (if it doesn't first time lift it up slightly first). Save the cartridge for future refill and the cartridge you want to put in you hold the same way and again from the bottom just literally slide it in. You should be able to click it in once it is all the way - this indicates it is in correctly, the printer should now run a test print.