If you check hotspotsystem they have step by step guides, however I don’t think your hardware is officially supported. That just means you will need to try it, like JTRTech said if you can get ddwrt or openwrt on it, then you can just follow the generic guides on hotspotsystem on how to install the hotspot under those firmwares. As I recall ddwrt has built in support for hotspot and you just need to enter some details for hotspotsystem to get it working, but I just read that - when I did it, I used the supported hardware.
I would point out though, it is quite advanced and time consuming, and you could brick your router very easily if you are not careful.
I would suggest you just take an easier route - buy a TP-Link TL-WR841N, its a cheap router (you can get for less than $20 USD from Amazon) and is supported by hotspotsystem. Then just follow the guide, download their custom firmware from the link on that page and you should have it working without too much trouble. This is the exact way I set one up for a client before, only difference was I used the slightly more expensive TP-Link router. On a side note, I use the TP-Link TL-WR841N in my office and it is a good router, works fine and actually better than one I had before that was 3x the price.