Practice. I have been tying for years. It takes a long time to get the hang of. If you want, there are fly tying video apps that work well. My favorite is called fly guide. And ask questions when you need help.
On FlyFlasher.com you can find 33,972 flies from all over the world. Flash your own fly patterns, upload your current work or search for inspiration. The flies are tagged, so you easily can search for them.