Hi
If you are going to download it, you will need to download an ISO file and then use ImgBurn software to burn it to a DVD.
The DVD can be used to install Windows 10 TP to a separate drive.
If you get Windows 10 TP through the store as an upgrade is will overwrite your Windows 8 installation.
If you decide to go the dual boot route make sure you name the partition something like "Windows 10" and write down the size of the partition as well.
When the install process asks you where you want to install Windows 10 make sure that the size of the drive matches the partition you created, (it may show as a little smaller then the size you made it).
But if it's a 200 Gb drive and your C:\ drive is 700 you shouldn't get them confused.
http://windows.microsoft.com/en-us/windows/preview-iso
Mike
There are some drawbacks to running it in VM Ware.
It will run slower, (my experience) and you won't have access to your software and files from it.
I wanted to use Windows 10 the way I did my main OS, so after trying it in VM, I undid it and dual booted.
I've found that a lot of my software installed in Windows 8 would still run in Windows 10 TP without being reinstalled.