WiringPi has been deprecated for several years now.
If you really have to use a Pi as your client device (a very bad choice in my opinion) then you’ll need to use Python of NodeJS, but I’m not sure if those libraries have been updated to work with Blynk IoT.
Another alternative is to use Node-Red and the Blynk plug-in for Node-Red.
No, simply installing it from the Palette Manager should be all you need to do. Are the Blynk IoT nodes now appearing when you scroll down the left hand side, or type “Blynk” in the “Filter Nodes” box?