I love electronics and DIY project but I’m new and beginner in experimenting with it, So I’m sorry if I’m asking something stupid.
I have old routers and I heard about OpenWRT and dd-wrt and customizing the router firmware so I was carouse to try
I got my old routers and searched I the databases of the custom firmware sites to find combatable on and I found a combatable flash file with my TP-Link TL-WR741N/ND v1
and I flashed it successfully, And you can see In the photos I have added a small fan to help cooling it and was trying to retrace the board so I can attach the fan in the correct place in the board and not just use another adaptor but that’s not important now. 
The important thing that there is no space at all in this router rom to install any packages and I’m new in it so I don’t have any idea what I can do with this custom router
So I need a help in the space problem and it does not have usb port but I saw on a blog that the 4 dots called SJ1 are serial port so maybe these port can help with something but I can’t totally understand how it works
And I need ideas what I can do with this custom router
sorry if I wrote a lot and sorry again if I ask about something stupid but I’m learning 
Thanks guys 
Did you buy the product from sparkfun?
We won’t have much advice, but I follow a guy on youtube named Matt Brown that does reverse engineering for routers and such and uses them for custom projects; I’d watch a few of his videos and go from there (he usually uses the 4 serial pins you mentioned to gain access)
No It was our home’s old router
Ok I will do
Thank you so much for the advice. I really appreciate it 
It is a linux system and could in principle run standard linux applications compiled for that particular processor.
But you would probably have more fun with something like the Pi Zero W or W 2, a full blown linux system the size of a stick of gum with an SD drive, that runs out of the box and costs only $15. Which incidentally can be turned into a wireless router with standard linux router code.
I second the idea of making a RaspberryPi into a router/access point. You can use OpenWRT for that, but you can also use RaspAP and there’s a project called HostAPD and software called Webmin which sounds good. It would be nice if you could upgrade the router with something from Sparkfun, but it’s probably not possible.
I can let you in on a secret, though: Consumer wifi routers stink! They aren’t even good at the job they’re supposed to do! All of the branded routers are junk, and there’s not much you can do with them ie: repurpose the hardware. Putting a huge fan won’t help, it won’t do anything where it might overheat, other limitations prevent that.
If you want to do anything that Sparkfun forums can help you with, you need to have a Sparkfun product. Any raspberry pi, any of them will do. Please don’t lose your enthusiasm, but you should have consulted someone before you put a fan on a router. Certainly RPi’s
get hot with intensive operations and, at least the larger ones could benefit from a mod like yours, but unfortunately, as-is, your project is like putting lipstick on a pig.