Not able to run selenium script through testng

I have written a simple script in selenium. I am using Testng. I created a xml file where i mentioned suit name and class name. Xml file code is as

              <?xml version="1.0" encoding="UTF-8"?>

                    <suite name='Suit1' verbose="3" parallel="methods">
                       <test name="Wiki">
                          <classes>
                            <class name="additional.wikipediaTEst"/>
                          </classes>
                        </test>
                     </suite>

Now when i try to run this by right clicking inside xml file, text box for selecting suite is disabled.

How this would be enable.