To copy a Campaign to another account, click the dropdown arrow on the right hand side of the campaign and click Copy to. Dependant on your user permissions, you'll be able to copy this to anyone in your Group or Client. To find out how to copy in your own account, click here.
This will open the Copy Campaign To Another User window. From here you can rename the campaign title, enter the name or username of the account and the added option of deleting the campaign from your account after it has been copied.
Once completed, click Copy to complete the action.