Use a Linux Live CD
In VMWARE create a Ubuntu machine with a working internet connection
Boot with LiveCD
LiveCD needs 2048mb memory to boot (needed for chromium)
Navigate and download from https://downloads.openwrt.org/chaos_calmer/15.05/x86/
I used /chaos_calmer/15.05/x86/generic/openwrt-15.05-x86-generic-combined-ext4.img.gz
dd if=openwrt-15.05-x86-generic-combined-ext4.img of=/dev/hda
reboot / shutdown
change / add network adapters
First network adapter needs to be in the 192.168.1.0 / 24 range and is the LAN side of Openwrt
Second network adapter is the WAN side of Openwrt (I made a direct connection to my home network)
Changed my virtual machine to 256mb and 1 processor and removed all unnecessary things and the cd-rom.
Then navigate to 192.168.1.1 this is the default network ip of openwrt.