I have a onn roku 32in and I bought a digital antenna at walmart you know the flat kind and I can't pick up 1 channel is there a special antenna I need?
There's no such thing as a "digital antenna". That's all marketing hype; don't get sucked in. Some HDTV channels have moved to the UHF spectrum while others remain on the VHF spectrum, so the antenna you get does make a difference, but it varies significantly by where you are. I need an antenna that can receive both UHF and VHF because about half the channels I get are on each one and the direction I point the antenna makes a huge difference.
You can use something like https://www.tvfool.com to see what channels should be available to you and what kind of antenna you may need.