Typically those devices are mounted externally, on poles.
Two antennas are also mounted higher on the pole and they are connected with a (short) coaxial cable that is inserted on the connectors and then makes a small loop downwards, sitting in the sort of grooves/gaps in the cover.
See:
http://forum.mikrotik.com/t/wap-coverage-picture-included/179859/1
In emergency or for configuration on the bench also “normal” straight antennas can be used, but obviously without cover, and that would IMHO be an issue for outside usage.
And on the other hand two straight antennas so close won’t likely be very efficient.
You would have (probably) been better served by Wap Ax (which is the “natural” successor to the wap AC):
https://mikrotik.com/product/wap_ax