As I said when I have the time I will add some quick tutorials. I will also update the help files for genwall the next days.
So here it comes:

USB LAN Connection Windows 7 Internet from N900

Prerequirements usb lan:
[PC]
driver e.g. from madde


Connect a windows system with usb lan:

1. [N900] connect to internet wifi/gprs/bt-pan
2. [N900] genwall {route-usb} click module button and load Windows module
3. [N900] genwall {route-usb} configure the network and dhcp addresses choose dnsmasq=forward and save settings
4. [N900-PC] connect the usb cable
5. [N900] genwall {route-usb} click the start button
6. [PC] look if you get a dhcp address
7. [N900] make iptable rules to forward network see next list

[N900] forwarding

{local-basics}

• Select wan device gprs/bnep0/wlan
• I would "accept connection from local machine"... makes live easier
• If you want to connect from pc->N900 without openning ports. I would also recommend to "Accept connection from local lan".

{for/out-forwarding}

• Activate forwarding and set lan device to usb
• Masquerade wan device should be active

{local-basics}

• gen rules
• push the start button

In case you want forward/open ports to your pc
{for/out-ports}
Before you generate the rules and start the firewall script you need to put your pc ip, the port and protocol then push the add button.