change the Autosave Interval

I would like to change the Autosave Interval and Post Revisions in WordPress. I can barely write anything as it is autosaving every 3 secs, and when I Publish, it keeps reverting back to an autosaved version. I found a plugin that seems to have fixed the revisions problem, but autosave is a hassle!

I tried adding the code: define(‘AUTOSAVE_INTERVAL’, 600 );
to my wp-config.php file, but I can’t save the change.

I’m new to this stuff so any “simple” instructions would be greatly appreciated.