How to modify the static text in the dialog?

Thank you

If you added a user-define dialog,you can modify the text from INI file.
Example:
WriteINIStr "$PLUGINSDIR\UserDefine.ini" "Field 5" "State" "newtext"

It depends on what you want to change. Provided you know the handle of the control you want to change, you should be able to handle most changes using a SendMessage command:

SendMessage $R0 ${WM_SETTEXT} 0 "STR:new text here"

In the above example, $R0 is the window handle. (The example requires that you include WinMessages.nsh in your script.)

Thans to Comperio.
but how to get window handle?

i.e. the title of welcomepage.

If you want to change the heading texts on the Welcome page:

!define MUI_PAGE_HEADER_TEXT "my text"
!insertmacro MUI_PAGE_WELCOME

It's in the Modern UI manual... You should read it more thoroughly.

-Stu