mesh nodes have ethernet port.

1. if you already have existing mesh network, you can add new mesh node right next to the DVR rack, connected by ethernet cable.

2. if you have not an existing mesh network, your can set up a new mesh network which includes a node next to your DVR (like above), and another node next to your fibre router.
(a) your can switch off existing wifi service by your standalone Access Point and let the new mesh network take over the same wireless SSID and password (your existing user devices might need help to rejoin wifi network), DVR and user will share same wifi network, OR,
(b) retain existing wifi service and Access Point; set up the new mesh as a separate network using different wireless SSID (and password), DVR will use separate wifi than user devices.