Include html on wordpress main index page only?

I’m new to wordpress, so forgive me if this is really basic.

I’d like to use some sort of conditional to use a different template or a conditional to include blocks of html on the main wordpress index page only (but not on any other wordpress sub-pages.)

The idea is that I want to integrate wordpress with an existing website and to retain some existing static homepage elements that tie in with others parts of the site, but use wordpress to maintain news items on the site, and have these news items appear on the index. Everything else on the index can be simply included as static html if I can figure out how to do this with wordpress for the main index page only.

Is there an easy way to do this?

Many thanks.