Hi there Monikah,
Yeah that's right, they usually give you Provera to bring on AF if you have absent/very long cycles.
It is totally an individual thing to how well you will respond to Clomid, usually I think they prescribe you Clomid for days 2-6, days 3-7 or days 5-9 of your cycle, depending on how long your cycles normally are.
For ovulation, from what I've been told/read etc, you can ovulate anywhere from day 11 to day 20 of your cycle.
My gynae has me on days 2-6, with Provera to bring on AF (usually 10-12 days of Provera then AF arrives within 3 days of the last pill).
Hope that helps!
Good luck