Step One: Go to your ask page (YOURURL.tumblr.com/ask)
Step Two: VIEW SOURCE CODE for the page. RIGHT CLICK> VIEW PAGE SOURCE
Step Three: Scroll down and find the code to your ask box. Faster way: CTRL+F and look for the title of your ask box, the code is right next to it. Copy this code.
Step Four: Go to your customize page, and make a new page, name it whatever you want.
Step Five: Add your questions and answers. Then hit the HTML button and paste the code that you copied from Step Three under all your questions and answers.
Step Six: Hit SAVE PAGE. Then in your HTML code for your theme, under your navigation type “/NAMEOFFAQPAGE” in the code and you have your faq page.