Its very easy, If you would like to generate self signed certificate from IIS 8 you can follow the steps . Before that I just what to tell you that, you should know what exactly self signed certificate do?. So Here we can discuss about how to generate self signed certificate from IIS 8?
1) Open IIS manager -> goto RUN type inetmgr.
2) Double lick on the Server Certificate (ref.below given image).
3) In this new window you could see Actions in right side.In that sections click on Create Self-Signed Certificate (ref.below given image).
4) Give any friendly name for your certificate, then click OK . Your certificate has been generated successfully.
Click here to see how to export a cerificate from IIS
— thank you !!!