I'm assuming that the 3102 is being used on the same LAN as the 3CX server and is "factory fresh", or a factory reset was done before you started.
OK...if you don't plan on using the router "part" of the 3102 it can be disabled and the yellow Ethernet port can be used for another device on your network. Before you do that, if you haven't already, on the WAN Setup page set Enable WAN Web Server to "yes". This allows you to access the device through the blue port using the IP address assigned to the 3102. You can set the NTP server(s) in there too.
Moving on...
Under Voice/SIP RTP Parameters, change RTP packet size to 0.020
Save the settings
On the Regional TAB, at the bottom, you can set your time zone. There are also daylight rules that can be set later depending on where you are. The Caller ID Method is also set here, default is Bellcore for North America. If you aren't located in NA, you may have to re-visit these settings.
Save your changes
On the PSTN Line tab...
You don't need an Outbound Proxy, it probably won't hurt, but it can be left blank. Which means Use OB proxy in Dialog can be NO
Register expires can be left at 3600 (the default) if you wish, or shortened it to the 300 you have, 3Cx will tell the 3102 when to re-register.
I have Use Auth ID at NO, and it works just fine, Auth ID is datafilled, as you have done.
Go down to DialPlans
change dialplan 8 (3CX originally chose 8 for some reason, it really doesn't matter) to (S0<:10004>) , that is a zero after the S
Under PSTN-To-VoIP Gateway Setup...You already have dial plan 8 selected, that refers to the entry above.
Under FXO Timer Values...If you are in North America using Bellcore CID, change PSTN Answer delay to 3 or the CID information will not be collected (between the first and second ring) before the call is passed to 3CX.
Save the settings.
If you don't plan on using the Line 1 on the 3102, you should probably disable it
Those are the basic settings. there are things that can be, and may have to be tweaked depending on your location. When testing, make use of the 3CX Activity Log to see what is happening with the calls. Incoming calls get "forwarded" to 3CX" 10004 (in your case) using dialplan 8. Outgoing calls are sent from 3CX to the IP and port of the gateway, that is why the port used (5062) must be in the 3CX trunk settings. Registration alone does not guarantee that call will reach the gateway, unlike an ATA.
If you have issues, post back and we will get it working.