These routers have two passwords. One is for control and security of the WiFi, and the other is for administration.
If you set the admin password (for root user by default), it disables telnet, so far as I am aware. If you could connect over telnet, this also means that it wasn't set previously.
Now, your URL for the web admin panel (LuCi) is possibly wrong. Omit the http:// or any preceding crud, and just type in the straight IP into your web browser. If that works, go to the tabs up top until you find one with WiFi in the dropdown menu, click, and edit the OpenWrt access point on that page. The bottom half should have the settings for security, but you need the click the tab about halfway down the page to access it. Set to wpa2-psk and enter a security key. Save and apply.
The solution, if that didn't work, is to download the standalone program PUTTY, and use SSH (on port 22) to get into the device instead. The IP (assuming you are directly connected to the router by ethernet or WiFi) is 192.168.1.1, the username is root, and the password will be the one you set.
To secure the WiFi, you will need to modify the files or use UCI (or install LuCi for web management), but I don't know the method for first two. Check the recipes or howtos under the advanced setup guide. (If you have a wad of space, perhaps try opkg install luci, but YMMV) Checking space is done by df -h. Ignore the number that appears under /tmp. That's ram, and won't help.
If LuCi was installed before as a part of the image, and doesn't seem to be working now (even with the fixed link), once you get into the ssh console, type factory_reset, and enter, followed by reboot -f, and enter (These are seperate commands). This will reset the router entirely, deleting installed programs and settings. You will now be able to go to the web server at the IP you mentioned and edit manually. THIS ONLY APPLIES IF YOU KNOW LUCI IS INSTALLED, AND IT ISN'T WORKING. To check if it is installed, do opkg list-installed and read the output to see if a LuCi package is present. This assumes that you have not installed it manually just now, in which case it will be working.
TL;DR: Telnet is whacked, since you set a password. You need to connect over SSH now, so download Putty http://www.chiark.greenend.org.uk/~sgta … nload.html and use it, with your new password, to get back into the router. Then check if LuCi is installed in the first place. If not, you need to learn some linux talk and modify some files I don't understand to encrypt the WiFi. If LuCi was already installed, on the other hand, it will make your life much easier. Toss the Http out of the address and see if that works now.
(Last edited by rdragonrydr on 25 Jun 2016, 04:13)