Step-by-step instructions for installing the Dreamwidth server code can be found at Dreamwidth Scratch Installation. The wiki category contains helpful information. You almost certainly want to read Suggested Server Requirements.
If you run into problems during the install process -- and you probably will; we're painfully aware that the installation process is neither easy nor well-documented yet -- the dw_dev community is eager to help! If you don't have a Dreamwidth account but want to get involved in development, or want to run your own Dreamwidth installation, you can email denise (firstname.lastname@example.org) or mark (email@example.com) for an invite code.
You'll find some useful tips and configurations in the Category: Production category, including details of Dreamwidth's setup and various sysadmin reference pages.