how to insert components (option button) in uninstaller?

[Sumathy]

When the uninstaller is run, it should prompt the user with a choice to "Remove some files " or "Keep some files"

I dont how to insert following code to the existing nsi file


!include "Sections.nsh"

; Pages
Page components
Page instfiles


Section "Dont Remove files" g1o1
MessageBox MB_OK "Files are not removed"
SectionEnd

Section /o "Remove files" g1o2
MessageBox MB_OK "Files are removed"
SectionEnd

Function onInit
StrCpy $1 ${g1o1} ; Group 1 - Option 1 is selected by default
FunctionEnd

Function onSelChange
!insertmacro StartRadioButtons $1
!insertmacro RadioButton ${g1o1}
!insertmacro RadioButton ${g1o2}
!insertmacro EndRadioButtons
FunctionEnd

Please help
I am new to NSIS.