Add elements to a group

How to add elements (or a group) to another group already created? have they to be exploded?

I would use Edit>Cut on the entities you want to add to the group, then open the group for editing and use Edit>Paste in place. Rarely should you ever find a need to explode a component or group after you’ve created it unless it is intended as a temporary thing.

Thank you very much Dave.
very usefull answer (sorry my not too much correct English)