Step-by-step instructions for installing the Dreamwidth server code can be found at Dreamwidth Scratch Installation. The Category: Dreamwidth Installation 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.