Yes. You can install your IPTVV login on as many devices as you like, for example your living-room TV, a bedroom box, your phone, and a laptop. The same username, password, and server URL work on all of them.
The limit is on simultaneous streaming, not on installs. A connection is one device streaming at the same time, so a 2-connection plan lets 2 devices watch at once. If you try to play more streams than the number of connections you bought, one of the streams will simply pause.
If everyone in the household wants to watch different things at the same time, choose a plan with enough connections to cover them, or add more connections later from your account page.