You need eggs, a bowl for the content of the eggs, needles or pins, temporary tattoos originally meant to be used on children's arms but that look pretty and Easter-y, and a pair of scissors to cut the tattoos with.
Next step is to shake the egg. Technically, this is an optional step but if the yolk and white is scrambled inside the egg before you start blowing it out (yes, I said blowing) it'll be a lot easier to get out. Also, I'd rather have a mix of white and brown eggs like the tutorial I linked above uses but I couldn't find any white eggs anywhere and so I had to go au naturelle. Also, sincere apologies for my shabby nail polish!
Make a little hole at the bottom of the egg, and a larger hole at the top. The general rule is: the smaller the top-hole is, the prettier is your egg but also a lot more difficult to blow the contents out of. I found that making a hole with about 4mm diameter worked fine.
Place your mouth close to the bottom hole and blow. Warning; This is pretty soul-destroying and remember to take breathing-breaks because otherwise you could faint. (Imagine blowing up balloons and having that stubborn one that just won't inflate? Each egg is like blowing up ten of those balloons.)
Once the egg is empty, wash it in cold water and dry it. Then follow the instructions of your tattoos. I'm not fully immersed in the tattoo world so I can't say if all have the same instructions, but mine required you to cut out the tattoos, place them on the egg and stroke the back of the tattoos with a damp cloth. Tip: The bigger your motives are the less smooth it will look on the egg (due to the egg being round y'all). So cut as close to the lines that you can (although the white won't show up on your eggs) and the more inward angles your tattoo has, the better. That allows you to place the different parts properly on the round surface.
Wait for 20 seconds and then remove the tattoo sheets. Voila, an egg is decorated. Now repeat with the rest of your eggs. Once your done you can either tie strings in them and decorate your Easter tree (because you DO have an Easter tree, don't you?) or just keep them in a bowl. Either way, I'm very pleased. Time to relax and go paint those trampy nails.