Add additional Ram To esxi server !

Hi

I've a Esxi server with about 20 virtual machine on it , and the server has 16 GB ram . I want to add about 24 GB Ram to the server .

I've to turn off the server and add the RAM hardware to the server . but some of my friends told me that , on this way , the server will crash or will have some problem .

does it have any risk  ? and the esxi will handle the new hardware correctly ? which way will you suggest me to do ?

thanks alot