Setting up a multi-step, timed flow campaign - how do I do this?

I'm setting up a multi-step campaign and am unsure of how to do it.

The campaign starts with an e-mail that has a link directing recipients to a Landing Page. Those who fill out the form on the LP immediately receive a white paper. 3 weeks later, the same people will get a different white paper.

1) How do I set up the steps?

2) For the white papers, do I store these somewhere in Marketo or somehow use an outside link? Or is it better to send them to another LP with a download link?

Any help would be appreciated! We're pretty new at this and I've never set up a campaign of this type.