Don't forget to patch fixtures in your show before trying to create a group. To create a group, open your show and press at the top right of the groups view toolbar. Then select the "Group" button.
To be able to control your devices you will have to add them to a group. To do this, press the below the group and select the devices you want to associate with it.
Now your devices should light up. You can control their dimming directly by touching the knob or by pressing the group name to display the group control panel.
You can delete a group or edit its name by touching at the top right of the groups view toolbar.
Your group is now ready and allows you to change the color, dimmer, position and many other properties of your fixtures. Come and take a look at everything you can do in the group control panel.
Visit the documentation to control group's properties