Clickable header

Friends,

How to make a header logo clickable to main page?

I know that this question was already discussed here https://www.ads-software.com/support/topic/header-clickable-2?replies=2

But when I embedded the code in function.php (as advised) my site crashed with “Cannot modify header information” error.

Maybe there is some other way to do this?

Pls help.

Thanx