I have some problem with php page and site pls help

helloI found your site and i saw that it has lot of interesting stuff...i saw these mail is related to questions so sorry if i missunderstood and i'm sending on wrong mail.The problem i have i think is simple but i didn't find solutions on google or whatever, i have website that is working fine and it uses php for all files as i know...i made new page html or i can make it php but when i place it on server it doesn't recognize it.The new page that i created is howitworks.html and i would like to add that to my index page on the button HOWITWORKS.How to do that?Thanks,Misel