X-Frame-Options header is not set

My website is currently undergoing the pen-test before it can be host live. They acquired me to fix this problem:

“X-Frame-Options header is not included in the HTTP response to protect against ‘ClickJacking’ attacks”

My question is, how may i set the X-Frame-Options on my website?

Hi there

I just answered on this question in your initial ticket, please don’t duplicate tickets