This isn’t going to be very much of a tutorial, as there’s no pictures, but I’m going to do my best to explain how to draw nail art freehand. Unfortunately, it takes a bit of drawing skill, which is probably not something I can teach here!
If you want to put freehand art on your nails, and you are not good at drawing, your results won’t look great. However, there are a few cheater tips I can share with you:
1) Find a simple clip-art image of what you want to draw. Do a Google image search or look in a clip-art library. The image will be reduced to simpler lines and a few colors. For nail designs, a bold, easy-to-see image is the best. A tiny, detailed image is extremely difficult to get right. Think simple, stylized, and bold rather than intricate. Start simple and work your way up.
2) Try drawing the image (large size) on a piece of paper while looking at the clip art. Refine your drawing, still using the large size and change any bits you want to. Draw the image successively smaller until it’s the same size as you want it on your nail. If it looks bad on paper, it won’t look good on your nails. Take a few extra minutes to really get it right so you can draw with confidence on your nails.
3) Paint your nails with a light color so the nail art will stand out. I usually use white.
4) Use a Sharpie marker (careful, it can stain your nails!) or nail art pen to draw the image. You can draw a line, or a series of dots placed close together. Make the lines fairly thick and bold. After the image is dry, paint the background around the nail art a darker color to make the nail art stand out. Add color to your nail art design if you want, but make sure your polish is fairly translucent so it doesn’t cover the outlines of the image. It’s easier to use a small paintbrush than a typical nail polish brush to fill in details.
5) Seal with a topcoat! Most nail art pens are water-soluable.
6) Practice with some simple designs like a cactus or flower before you get more complex.