New Airport express user needs some help on setup. Thanks

With the AirPort Express Base Station (AX) connected back to the Netgear router by Ethernet, you can configure them both for a "roaming" network.

Roaming Network Setup

• Ref: See page 42 of the Apple AirPort Networks guide.
• Setup the Netgear connected to have both NAT & DHCP enabled. This should be its default settings.
• Setup the AX as a bridge. AirPort Utility > Select the AX > Manual Setup > Internet > Internet Connection > Connection Sharing: Off (Bridge Mode)
• For each router:
  • Connect to the same subnet of the Ethernet network.
  • Provide a unique Base Station Name.
  • The Network Name (SSID) should be identical.
  • If using security, use the same security type (WEP, WPA, etc.) and password. Note: It is highly recommended that you use WPA2 Personal for best bandwidth performance.
  • Make sure that the channel is set at least three channels apart from the next base station to prevent Wi-Fi interference.

Using MAC filtering is really not a security measure as "hidden" MAC addresses can easily be discovered and bypassed. However, if you feel this is important to you, the AirPorts implement this type of filtering a bit differently than other vendors. That is, the AirPort have an option for Timed Access using MAC filtering which may be a different implementation than your Netgear.

I think the solution for you is to set the Airport Express in bridge mode (through Airport Utility).

And you can restrict connection by MAC address through manual setup of the Airport Express.

Which version of the AirPort Utility are you using? The latest is: 5.5.2

That's the wrong option. The one you want, "Connection Sharing," is on the Internet > Internet Connection tab

Ok, here's the shot of my AirPort Express ...

This option would only be applicable if you were to extend this AirPort with another. Since this is not the case, you should leave this option disabled.

wireless network name (do i pick the same name as the main netgear routers wifi name or a different name as at the min i have a different name to my netgear router.)

Yes, you want to use the same Network Name (or SSID) at the Netgear's wireless network.

wireless sec: wpa2 pers

password: *** (do i use the same password as my netgear main router ? or a different password)

You want to use the same wireless security type and password as the Netgear's wireless network.

what happens if i use a different uisername and password will it then use a different connection ? i the wifi but if i use the same password and username it will extend my wireless strenth ?

If you configure the AirPort with another Network Name and Security Type/Password, then you will effectively, be running two separate wireless networks.