please help me

http://wiki.yetanotherforum.net/Installation%20Instructions.ashx 

Follow the documentation. once everything is properly setup open the /install dir in the web browser and follow the installation steps and your forum will be up and running. Let me know if you have any confusions.

how I can change web.config file ?

After you have put the downloaded YAF files on your web server. You can modify the app.config file, db.config file, mail.config file according to your setup.

i would like to run it from Visual Studio 2010 .......so under the solution what the format and what part I need to change ??:arrow:

If you run Yaf from Visual Studio Simply Download the Source Version of YAF, open the Project File and Press F5 to run YAF.

If you looking for an really easy installation you should try installing YAF via the Microsoft Web Platform Installer

http://www.microsoft.com/web/gallery/yetanotherforumnet.aspx 

If you use the YAF Version from the Links i posted Above you don't need that file, or if you try to upgrade from an older version you should read the Readme.html File that is included in the Download Packages.

There is a folder called "webconfigs" in the YetAnotherForum.NET folder. There is a File in that folder

"recommended-NET-web.config" copy it to the YetAnotherForum.NET and rename it to web.config, and delete any existing web.config if any exists.