The best way is to flash a new Image with the webif version already included.

You can try to update the webif in your image: go to dreamboxupdate, select the experimental feed for your hardware, download the "enigma2-plugin-extensions-webinterface_<version>.ipk" and install it via "ipkg install enigma2-plugin-extensions-webinterface_<version>.ipk".

But this will fail if enigma2 is to old...

Try to use dreamstream E2 0.4.0 (beta2) not dreamstream E2 0.4.0(beta10 )in this download