I dont have my omnia yet, but if you look around it is rather easy, because as i could see, a ipk file is already available for installation.
Information about how to install a ipk file on openwrt : OPKG Package Manager [Old OpenWrt Wiki]
So this should be done as follows
Step 1:
ssh to your omnia using a terminal, if you are on windows, you could use putty.
ssh <ipadress omnia>
Step 2:
opkg install https://github.com/k-szuster/luci-access-control/releases/download/v0.3.1/luci-app-access-control_0.3.1_all.ipk
Step 3: logout from ssh and go to the webinterface of the omnia…should be looking like this…
This is all theoretical and logically speaking, should work i guess.
Let me know if it worked or having any problems.