The first one is provided by the internet provider and is locked (no access to the setup). The Router has 4 lan ports + wireless. From LAN port 1 on this router I connect to the WAN port on my secound router/switch.
The secound router/switch has 24 LAN ports (but no wireless). I use this router to connect to computers, printers and NAS.
Now I have a number of wireless devices. They all connect to the first router because that one comes WIFI. I would the devices to be able to access data on the NAS (which is connected to the second router), but cannot get it to work.
Should be pretty easy. If everything else is good now, you have several choices.
The most simple and one that would not require you to access the first router settings would be to just add a wireless card to one of your computer linked via wired Ethernet and configure it as an ad hoc wireless connection on a second network and share you Internet connection either using ICS or by bridging the networks on the computer with both connections.
You could also just attach an AP or a router configured as a wireless access point to a port on the switch, and turn off its DHCP, and use different radio channel from the main router to avoid interference. I would lean towards the second option as it would not require the bridging computer to be on.
Is the NAS attached to the second router by a USB connection or a wired LAN port?
First a question, which router controls your network -- i.e. which router runs the DHCP server? If server one controls the network and runs the DHCP your LAN would show up, so it seems that your second router runs the DHCP server, and if your router has a second DHCP service your wired devices would not be accessible from wireless devices connected by router one.