To group and ungroup objects:
Select all the objects you want to group together. To select several items, hold down Shift while clicking everything you want to group. You also have the option to click and drag your mouse over everything you want to select.
Click the Group button on the top toolbar.
3. To ungroup a set of objects, click on them once, then click the Group button again.
You can also use the right-click menu to copy or group/ungroup when multiple objects are selected:
Here is a video tutorial: