domain mapping - addin new site domain names

hi, im a little unsure why to go after installing the domain mapping plugin.

how do i add the sites?
do i have to create a site in my main multi site first then map the actual new site domain name to the multisite newly created folder?

will i still be able to modify the mapped site just like any other multisite instal?

my first task would be to instal the same theme...how would i do this too?

here is my sites how i would like it...
lovestruckmedia.com (multisite current)
--lovestruckhosting.com (domain to be mapped)
-- lovestruckgraphicdesign.com (domain to be mapped)

-- then i need to install the same theme as lovestruckmedia to both of them...is that possible form the network admin area?