Hi, it says I must put my meta tags at the HEAD of my HTML document, where can I find that?

Just before the BODY section. That may not help. If you have to ask, you are probably using some freak editor that hides things like that for you.

For instance, if you use the Geocities PageBuilder, I believe it is Format-Advanced Page Properties.

But if you want to do something more advanced than what your editor normally permits, perhaps a more advanced way of building webpages is called for?

if you are using wesite wizard,
go to website details,
place your keywords and all there
and publish!!
they become your meta tags!!