Network switch and router questions

I recently got a TP link 8-port gigabit switch as well as a Cisco Linksys EA3500 router. I have a lot of computers and machines that need ethernet but was also looking to better my wifi signal in my part of the house. Aside from the houses "main" router, runs 1 ethernet cable to my room.

 

Here is where the questions begin:

1) Should I take the ethernet from the main router and first plug it into the switch or the router?

2) How/where can I find the information to make my new router into a switch/wireless access point?

3) If I were to connect an external hard drive via usb to the access point, how would I best secure it so that only I can put files onto it, but may allow others to read files from it?

 

Thank you, I am still looking for guides elsewhere online but wanted your thoughts and help as well!

here is router set to AP outline

http://www.smallnetbuilder.com/wireless/wireless-basics/30338-how-to-convert-a-wireless-router-into-an-access-point

You will want to do this first before connecting it to your existing router

If i correctly understand what you want ...I think you want the topology to look like this

 

Main Router ---Ethernet--| Next Room |-----> Switch -----Ethernet-----> router converted to AP.

Thank you a bunch man, this really helped!!

No Problem! I think that NTFS (windows file security) might be enough enough its not encrypted but it should prevent people on your network from messing with your stuff. If you think you need something more I'm sure other people on the forum could probably answer better than I.

One thing you should check on the AP is their channels. You may be able to get a little extra speed by finding a less used channel of WiFi in your area. Also disable UPnP in the AP because devices may get confused as to which UPnP device is the real gateway.