There is lots of documentation on how to do this. You could start by looking in the
GNS3 HOWTOs, or under the
Documentation tab off the main GNS3 home page - in particular the
Connection GNS3 to Real Networks article.
There is also a section in the book
GNS3 Network Simulation Guide from PACKT publishing that takes you through a mini project called
Connecting your GNS3 router to your LAN which would help you achieve what you are trying to do.
[Disclaimer. I am the author of the
GNS3 Network Simulation Guide]
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RedNectarhttp://rednectar.net@rednectarchrisGNS3 WorkBench-a VMware image of Ubuntu with GNS3 and VPCS installed and a collection of exercises/labs