There are three options to create a group: From the list of groups, from the list of jobs or using the Duplicate button in a job.
From the list of groups
Once you're in your list of groups, simply click on 'Add a group'.
In the popup that opens, you will be able to define the name and colour of your new group, and also select the jobs you would like to put in it.
From the list of jobs
In your list of jobs, you can drag and drop jobs into each other to put them together in a group.
When doing so, the system will show you (with a green line on the left) in which jobs you can drag and drop a job. It will then open a popup in which you can define the name and colour of your new group.
You can also select all the jobs you would like to put together in a group in your list of jobs and click on Actions > Create group. This will open the same popup as above, in which you can define the name and colour of the new group.
Using the Duplicate button
In your jobs, you can use the Duplicate button to create a new group with these two jobs. Just toggle the corresponding option (this action will add a field in which you can define the name of this new group).
If the job you want to duplicate already belongs to a group, you will also have the possibility to add the duplicated job to the group.