Question about Yamaha Wxa-50

Yes, you can; the Yamaha WXA-50 (which, by the way, sounds excellent and can be used universally thanks to MusicCast) has both coaxial and optical digital, but also analogue (RCA) connections for this purpose. Only HDMI interfaces are not available. Most better CD/DVD/BD players can be connected to the WXA-50 in one way or another. If you have a TV but not yet an optical drive, I would recommend a current BD player from the same manufacturer (as that of the TV). If you don't have a TV, you can also use a CD player that matches the Yamaha optically, but of course sounds good. I can think of the Pro-Ject CD Box S2 player, for example.
A possible alternative: Yamaha MCR-N870DAB (Silver/Black, 2 x 70W, WLAN, Bluetooth, CD)

Hi. I don't assume you mean a USB drive because I don't think this will work. The USB port on the Yamaha will only take USB STICK or HDD in my opinion. Might have to go with a guaranteed plug and play drive, but I'm sceptical. There are also CD players that play a whole range of digital formats. An entry-level CD player goes well with the amplifier. I have had good experiences with the Marantz PM5005, available here at Digitec. It can be connected to the Yamaha via RCA or optical cable. The combination could fit well. Greetings