The workbench is enabled by setting the workbench-enabled setting to true in the ApplicationSettings.properties file and restarting the webapp or Tomcat
There are two further workbench settings to be aware of - max-total-workbench-assets and max-concurrent-workbench-users. These control the number of assets that each workbench can contain and the number of concurrent workbenches that can be setup. These are used to control the amount of memory that workbench can use (because assets added to workbenches are stored and edited in memory - the more assets in workbench the more memory is being used).
The attributes that can be edited through workbench needs to be configured via the display attributes admin pages. Login to your Asset Bank as an admin user and go to Admin > Attributes > Display Attributes > Workbench. Select the attributes that users should be able to edit and add them to the group. If this step isn't performed then no attributes will be shown when editing assets on the workbench.