There are several resources available for the above questions that I will do my best to provide below.
+ When running the installation. Please run the installation as an administrator. This allows the installation to access all the necessary folders during the installation process.
Information on signing into TSM can be found here: Sign in to Tableau Services Manager Web UI - Tableau
Additionally, if the Tableau Server is not installed properly, there could be issues with launching the TSM Web UI. Were any error experienced during the installation process?
Hope this helps!