How did you connect the box to the TV?
If it has HDMI or AV connections use those. Select that input on the TV. The box remote will let you run a channel scan and after that you will change channels with that remote.
If you connected it to the RF antenna connection then select the channel set on the back of the box (usually 3 or 4). Run the scan.
I have a vintage Toshiba tv with built in DVD player. LED old, but great picture. I bought at thrift store - traveling in Florida hooked up old style rabbit ears stuck it to wall and walla 15 free channels. Tried 50$ flat antenna - didnt work. Tried 15$ ears. Works great!!!