I am worried knowing my luck I will buy all the equipment and this wireless issue will be my nemesis!
Honestly I was in the same boat as you and worried about getting mine connected to wifi, but it literally was a breeze. If your using fusion follow these steps.
1. BEFORE setting ups apex next to your tank, take apex "brain" over to your wireless router and connect it hard-wired via ethernet.
2. Next plug it into EB8 and then finally plug EB8 into the wall.
3. Let everything get "started up" and then using a computer connected to THE SAME network via wifi (used my laptop) log into fusion, and using apex display get your "fusion token"
4. This should allow you to have apex all linked up with fusion and ready to go
5. Next I plugged the wireless extender (Belkin one above) into an outlet in the same room as my router and followed their quick instructions for connecting to my home wireless network, entered password and was all set up there.
6. Finally I unplugged the apex from the wall and router, moved it all down to my tank room, plugged in the wireless extender next to tank, and then ran a single ethernet cord for the extender to the apex "brain". Just need to make sure you have an open outlet for the wireless extender near the tank that is NOT the EB8 outlets... I have several extra outlets on my GFCI behind the tank, so I plugged it into that.
7. Plug brain unit into EB8, plus EB8 into power and let it all start back up.
8. Should be ready to go, and have complete access to Fusion and now have a wireless apex controller.
It def sounds daunting at first, but honestly following these above steps allowed me to set up my apex (for wireless) in around 5 min total. Now programming the apex takes some serious time as you have to plan out everything you want it controlling etc, but thats where the fun tinkering begins

good luck and let us know how it goes