1. Download Redhat as an .iso (for example - there are many other options)
2. Create a new VM in VMWare Workstation. Declare type= "Redhat".
3. Set up your disk, CPU, RAM, etc for the new VM.
4. Assign the CD-ROM to your Redhat .iso
5. Start the VM.
You might have to hit "esc" to make the VM boot from your "cd-rom"
6. Install Redhat.
7. Voila! Done.