Some extensions may need the help of a professional beautician, but most hair extensions are getting much easier to use, especially K-tip and I-tip extensions which are made to be easily accessible by anybody. All you really need is a good friend to help out.
Here are some helpful instructional videos from YouTube that may be of use to those who have questions.
Needs: K-Tip hair, Heating Iron
Needs: Weft Hair, Clamping Tool, and Ring