Check out this tutorial :
https://www.howtogeek.com/98408/how-to-install-additional-software-on-your-router-dd-wrt/ or to be more specific, which of this files re the right ones?! http://archive.openwrt.org/snapshots/trunk/
How to geek is telling me to use http://downloads.openwrt.org/snapshots/trunk/ar71xx/packages/opkg_618-2_ar71xx.ipk but the file folder "packages" isn`t there anymore.