<HTML>
Put <HTML> at the beginning and end of your document. Everything in the document goes inside <HTML>, except that <!DOCTYPE ...> (if you choose to use it) goes just before <HTML>.
<!DOCTYPE ...>
For example, this code produces this little page:
<HTML> <HEAD> <TITLE>My Home Page</TITLE> </HEAD> <BODY> <H1>My Home Page</H1> Hi there! </BODY> </HTML>
Within <HTML> there are two major sections: <HEAD>, and <BODY ...>.
<HEAD>
<BODY ...>
<HTMLPLUS ...> >>>
<HTMLPLUS ...>