Hi,
Did you read datasheet? Usually there is a chapter "therory of operation" where you can find a formula. Also there should be some kind of typical values - maybe in a "selecting capacitor/resistor value" chapter.
Additionally there should be some charts where you can find the relationship between R, C and frequency.
Either we or you have to read datasheet... please go through it.
If you don't find a solution, please write where exately you encounter the problem.
Klaus