1. Backup your website and database. I zip up everything in the dnn website folder and just copy my dnn.mdf file.
2. Make a copy of your connectionStringValue from your web.config file
   <configuration>
      <connectionStrings>
       <add
         name="SiteSqlServer"
         connectionString="connectionStringValue"
         providerName="System.Data.SqlClient" />
     </connectionStrings>
   </configuration>
3. Make a copy of your validationKey and decryptionKey from your web.config file
   <configuration>
     <system.web>
       <machineKey
         validationKey="key1"
         decryptionKey="key2"
         decryption="3DES"
         validation="SHA1"/>
     </system.web>
   </configuration>
4. Make a copy of your objectQualifier and databaseOwner Keys if they have been altered (or anything else you may have altered in web.config you want to keep)
   <configuration>
       <data
         defaultProvider="SqlDataProvider">
         <providers>
           <clear/>
           <add
             name="SqlDataProvider"
             type="DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider"
             connectionStringName="SiteSqlServer"
             upgradeConnectionString=""
             providerPath="~\Providers\DataProviders\SqlDataProvider\"
             objectQualifier="dnn_"
             databaseOwner="dbo"/>
         </providers>
       </data>
   </configuration>
5. Download and unzip the upgrade file into your dotnetnuke website.
6. Copy the release.config or development.config file to web.config, and update the new web.config with values from steps 2-4
7. Visit your website at http:\\localhost\dnnWebsite and you should be able to update. If you get a warning at this point, you'll likely want to solve the problem before clicking update.
   

thanks a lot for the help.I could upgrade my site successfully,but i wanted to know where do we find the private folders now on this new version ? also do i need to do the module upgrade too ?

i already had version 4.3.0 and i upgraded it to 4.3.3.do i need to upgrade each module for this too.cause in the install guide they have just mentioned about upgrade of mudules from version 3.x to 4.also with the 4.3.3 final version there is this zip folder for module upgrade in which we have a module upgrade wizard.exe file ,what is that for ? cause the process u have mentioned is very different and we will have to load one module at a time by this .i am bit confused in this...