How to connect a mixer to an audio interface?

You description lacks one vital piece of hardware: An audio interface. I’m not that acquainted with your laptop, it may have Audio Input connectors that you could use in a pinch. However, computers built in audio interfaces are regularly of pretty poor quality, so I’d recommend that you invest in an external one. If you only will record two channels (which your description hints at), a relatively simple one like this one could serve you well:
http://www.steinberg.net/en/products/audio_interfaces/ur_serie/modelle/ur22.html

If you need to record multiple channels simultaneously, thje prices obviously goes up:

http://www.steinberg.net/en/products/audio_interfaces/mr_serie/start.html

Up to three MR816’s can be daisy-chained together, giving you a total of 48 (16 analog & 16 digital) inputs.

This is an unusual question. Most would have asked for the maximum features. Anyway, if all you want to do is making stereo (or mono) recordings of your sermons, I would recommend a Stereo recorder such as WaveLab. You won’t have any use of the multitrack recording capabilities of Cubase.

WaveLab Elements 8 would probably be a good choice. It’s inexpensive, but I believe it will cover your needs:
http://www.steinberg.net/en/products/wavelab/line_up/wavelab_elements_8.html
You can download a trial version here: Try WaveLab Now for 30 days | Steinberg

Yes. Provided that the receiver for the mic does have an output volume knob, you won’t even need a mixer.

  1. Connect the mic-receiver to an interface input. Either directly or through a mixer.
  2. Connect the interface to the computer or install the driver software. Some manufactures require you to connect the interface before installing the drivers, while others require that you do it the other way around. Consult the operations manual for the interface, for the correct procedure.
  3. Install and launch WaveLab Elements (or whatever recording software you will use).
  4. Before you can record anything, you must tell WLE about your audio interface and where you want the recorded audio to end up (as well as file format). Again, consult the operations manual for the correct procedure(s).

Hope this helps to get you going. Good luck.