Custom post types in main loop

I have searched for a tutorial on this, but nothing quite seems to address what I am hoping to do.

When viewing the main posts listing (index.php) I want to include my two custom post types (‘recipes’ and ‘events’). Meaning that instead of just seeing the latest posts, I would like to see the latest posts, recipes and events — all mixed together and shown in chronological order.

Can someone people tell me how to edit the loop so i can get this to work properly?