If you already have an installation of Serena Business Manager to which you plan to add Serena Development Control, you do not need to install a new system for Serena Development Manager. You do need to do the following:
Ensure that you are running a supported version of SBM as indicated in the Serena Development Manager Readme.
After installing the rest of the products in the suite, follow the post-installation configuration instructions for SBM.
Please continue to Installing Serena Development Control.