Go to Publish>Test as Add On and Configure a New Test. Testing your script will run the code on a doc of your choosing.
You should be able to take it from there. If you're still having trouble, read on.
To setup the test, you'll need to specify which Document, Form, or Spreadsheet you want to it to run on, and save the test. Then you can run the test (from the Test as Add On popup, by clicking the Test button after you've saved your test setup) and it will execute your code on that document/spreadsheet/form by opening a new tab with that doc and executing your code.
To share the script with others (beyond making them use this same process for themselves by copy/pasting your script in their own Script Editor) you'll need to publish it to the Web Store; to do that you need to do all this stuff.
Hope that helps!