Hi Rony,
These steps can help you:
1) Run VuGen and choose new script
2) Select AJAX protocol (for LR 9.1 and higher)
3) Fill the website page field
4) Start resording and perform needed actions
5) Stop recording (VuGen will generate the script)
6) Save script and invoke Controller
7) Create new scenario with your script (add 20 Vusers)

Run it
9) Invoke Analysis and load results (take a look into graphs for identification the bottlenecks)
Enjoy
