You can calculate wind direction from the component vectors U (x direction) and V (y direction).
Be aware though, U and V are relative to the WRF model grid, so they may need to be rotated to be relative to the earth. This can be achieved by
Uearth = U*cosalpha + V*sinalpha, and
Vearth = V*cosalpha - U*sinalpha.
Also, be aware that if you want to compare this to observations, these typically record the direction the wind is blowing from, in degrees from North, so you need to make sure you compute this from the component vectors.