Otsuki station

No. Fujikyu is not covered by Suica/Pasmo. But you can use it on the JR trains to Otsuki Station

does it mean that to reach Fujikyu Railway Kawaguchiko Station, I have to travel to Otsuki station first and transfer to the fujikyu railway train?

If so, can I buy the train ticket at otsuki station for fujikyu railway? How much does the ticket cost? Thanks!

does it mean that to reach Fujikyu Railway Kawaguchiko Station, I have to travel to Otsuki station first and transfer to the fujikyu railway train?

No. It is just one of your options. The other option, a direct bus from Shinjuku, is explained here:
http://www.japan-guide.com/e/e6905.html

If so, can I buy the train ticket at otsuki station for fujikyu railway? How much does the ticket cost?

Yes. It costs 1110 yen.

I have do go from Tokyo to Kawaguchiko the 1.10.08 and back the 4.10.08. I don't find a timetable for this time: Bus or train.
Thanks

For the train times go here:

http://www.hyperdia.com/cgi-english/hyperWeb.cgi

Enter your start station in Tokyo and your destination (Kawaguchiko). The fastest way is via Shinjuku.

I'd strongly recommend you to catch the direct expressway bus to Kawaguchiko from Shinjuku. It's 1,700 yen each way.

http://www.jnto.org.sg/news/47_1.pdf
http://www.jnto.org.sg/news/63_1.pdf