First Step:
Is your mainboard's BIOS new enough (ie., a version near or slightly after 7 Jul 2019) to support Ryzen 3rd gen CPUs? (If not, there will be no POST/power-on display)
Many in this predicament would need a 1st or 2nd gen Ryzen to be able to flash the BIOS to support the later version, unless your MB is one of the lucky few that support BIOS updates with no CPU installed...
FYI, you will need at least one RAM stick, and a functioning GPU installed, as since your CPU does not have integrated graphics support, the mainboard's HDMI/DVI would not be functional