Yes, you can easily invite somebody to join a contest.
You need to open the contest page and to click ‘invite’ at the right corner of the menu below the contest cover.
But make sure that the contest is hosted by VOUBS. Otherwise, inviting is not possible.
After clicking ‘invite’, you need to choose how you prefer to invite the user:
PP: Please, note that inviting a friend to contest and inviting a friend to VOUBS are totally different options.