Create a parting from ear to ear. Your first parting will be around the middle to top of the ear. It is easiest to use your fingers to part since they will always meet in the middle. Start with the narrower extensions that will fit in this area of the head (usually have two clips).
Tease the root to create a cushion for the extension clips. Use a hairspray or texture spray before teasing for extra grip. Insert the clips into the teased root and close clips.
Continue moving up the head, leaving some hair in between the previous extension and the next. As your head gets wider, you will use the wider extension pieces.
Use as many pieces as you need to create your desired result, and leave enough hair out on top and around your hairline to cover your extensions. Enjoy!