Adding a second menu but theme only supports one

I want to create a second menu on my website (in order to have multiple language support). I am using the fBiz theme but when customising, it says under ‘navigation’ that my theme only supports one menu. I have already created a second menu but the website will only show one. Is there a way to change this and make my theme support two or more menus? Ideally, I want to be able to set which menu to display on each page individually….