The only way to be a thelemite is to follow "Do What thou Wilt, Shall be the whole of The Law".
The first place you need to start is to read the core thelemic text- Liber Al vel Legis. After that I would say gain an interest in meditation, high magick, and yoga. Search for college of thelema and download the black pearl magazine for free, I also beleve in the continuum magazine is available.
I am a thelemite and so if you have any questions pm me, but remember I can only give you my perceptions of events and they may not necessarily be yours.