Steps to make it work:
1. Use FileZilla or similar and transfer .ipk file to "/var/volatile/tmp" in the receiver.
2. Start telnet. Login is root (password is not required), then type the following and press enter: opkg update && opkg install /tmp/*.ipk
In telnet, Type reboot.
Putting it in the tmp folder is just the first step. Telnet is used to install the file after it is put in the tmp folder.