To open the Publishing Task Manager select Publish in the File Menu, then click on Task Manager at the upper right to show the Task Manager page. Help+Manual includes a ready-made publishing task called "Common" for the three most common output formats.
A publishing task consists of a list of "actions". Each action is one publishing operation for your project. The action definition includes the output format (CHM, WebHelp, PDF etc.) and the output file name and path, whether you want to delete the temporary files and display the finished help automatically and the include options for conditional output. In addition to this, the actions can also include a list of variables you want to redefine for this specific task.
For full instructions, see Creating and editing tasks.