As above and you will have to set the 2nd display resolution to the native resolution of your RCA TV (check the manual). If you have the PC set too high it will show no signal or out of range.
You may also find that the TV will not detect the PC unless you select that input before booting it up. HDMI "handshakes" between devices but not always in the same time. Sometimes the PC has to be fully booted to show up sometimes the reverse. Sometimes you have to switch to another input and back to get them to see each other.