Open Power Options. you can do this either by clicking on the battery icon and choosing more power options or Press Win + I and click the Control Panel link,then power options
Click the ‘Choose what the power buttons do’ link to the left and then click ‘Change settings that are currently unavailable’.
Scroll down through the list of options and tick the Hibernate box before clicking the ‘Save changes’ button.
Thats all there is to it...Next time you bring up the power menu, the hibernate option will be there ready for you to use.