How I can modify the sampling frequency of ADC using cube mx configuration?

Hi everyone,

I use stm32 discovery and external sensor ("pulse sensor which used to measure the beats heart") connected to the card. I want to read the samples in the output of ADC. More precisely, I use cube MX for configuration. 

But, I need to modify the frequency of sampling (because it is very higher).  

should I use a timer to control the sampling rate and how I can fix the timer settings such as prescaler, counter according the desired sampling frequency?