So you are ordering a ID for the first time and you need to upload a file with your signature. This is how you can do it.
1st option: Use snapchat. I have heard lots of good things about this and it is pretty simple and also everyone has snapchat. Take a picture with your camera covered so the screen is black, not mostly black or your fingers only covered half the camera. When you have a black screen take the pen and pick white as the color. Now do your signature and save the photo to upload.
2nd option: Use printer paper and sharpie. Take your printer paper and sign it with your sharpie and making sure it isn't to thin. Then preferably you scan the paper or take a very good photo of the signature to upload.
3rd option: Use a signature app. There are apps where it give you a background and you sign and save it. If you do this please sign in black on a white background for the best results.