technically challenged peep in search of DNS advice

As explained in the title I have a question on a subject that might seem dumb to some. I have a hosting account on 1&1 that has a domain name going with it.

I also have another two domain names i have acquired through namecheap. My hosting allows me to point all my domains to that hosting account as long as i have space available to host all the files.

One of the domain names is my name. I want to use that with a single page wih an opt in form. The second one is my spanish domain for a project i have. The third domain is the first niche im going to be working on ( well, with 460 monthly globalsearches its probably more of a micro niche but I think i can bring good traffic to it nonetheless).

As I´m mostly testing on the spanish one at the moment, the focus is on the miro niche. I want to be able to point all three domains to the hosting account but I think I´m going the wong way about it. Supposedly i would need to have three directories ( one for each domain) and point each domain that way, or at least two directories and then host the third at root ( at the moment im hosting at root only).

How do I se this up? do i create subdomains and redirect the url, to the subdomains? do i domain mask them when redirecting? is there an easier way to do this im missing?

Im eading the help files and the pdf guides form the hosting account but im on information overload and can´t think straight. :confused:

Any help would be greatly appreciated