The motherboard's monitor ports will only work if you install a CPU which has a graphics chip (ie an APU) -- the Ryzen 3 isn't an APU - - - so you have to install a graphics card and plug your monitor in to that.
The motherboard's monitor ports will only work if you install a CPU which has a graphics chip (ie an APU) -- the Ryzen 3 isn't an APU - - - so you have to install a graphics card and plug your monitor in to that.