How to change the home page destination?

The short answer is that you can't. However what you can do is modify the content of the home page (i.e. Main.WebHome) so that it displays what you want. You have 3 techniques:

• Technique 1: Include the page you wish to display from the home page, e.g. have the following in Main.WebHome:
  {{include reference="MySpace.MyPage"/}}
• Technique 2: Redirect the home page to your page, using a script, e.g. have the following in Main.WebHome:
  {{velocity}}
  $response.sendRedirect($xwiki.getURL('MySpace.MYPage'))
  {{/velocity}}
• Technique 3: Modify the web.xml file to control what http://<yourserver>/ should redirect to. Specifically, edit WEB-INF/web.xml, locate the section with the servlet responsible for the redirect (the one with the line <servlet-class>com.xpn.xwiki.web.HomePageRedirectServlet</servlet-class>, and change that section to contain something like:
  <servlet>
   <servlet-name>redirectHomeServlet</servlet-name>
   <servlet-class>com.xpn.xwiki.web.HomePageRedirectServlet</servlet-class>
   <init-param>
     <param-name>homePage</param-name>
     <param-value>bin/MySpace/MyPage</param-value>
   </init-param>
  </servlet>
  {{code}}