The only way to do this so that the adjustments an structure are preserved is to export as a library and then import that library into the Aperture library on the iMac.
If all the images you want to move are under a single folder in the Aperture Library Inspector you can select that folder and then go to File->Export->Folder as new library...
Once the operation is done copy the new library to the iMac and do File->Import->Library.
The only thing you need to look out for is if the masters are referenced if they are there is an option in the export window telling Aperture to include the masters.
And yes, you export them to wherever you want, preferably somewhere which is accessible from both of your machines. In general (especially if you have a home network), you should be able to do it without any external devices (like external hard drive or DVD).
I have generally used my network (File sharing). From the first computer, I export things to a shared location on the second computer (across the network), and then use a second computer to import from that (local) directory. Obviously, you could also write from the first computer to that same computer, and then import across the network from the second computer, too. Or, export and import locally, using Finder to copy things across the network in the middle.
Since importing does modify your database, I tend to try to do those things locally. That is why I would prefer to export across the network (The export is only reading your Aperture database, not writing to it.)