Yes, Antoine,
getting started is the hardest part. I suggest you go through the process and check that you have all the hardware you need, including a number of spare needles, and plenty of painters' cardboard for making templates/patterns. The webbing I used for boltrope was actually called 2" seatbelt webbing at the US supplier we got our cloth, webbing and thread from.
http://www.rochfordsupply.com/
However, it is not 'real' seatbelt webbing. This one stretches very little, while I can imagine that the real seatbelt webbing is slightly more elastic (..but I could well be wrong on this...).
When you have collected all the stuff, you need, you will reach a point when you say:
NOW IS THE TIME!
Good luck,
Arne