you'll see 2 boxes one with available scripts(including the new ones you coded), click your script and click the right arrow to move it to the assigned box.
if your script does not appear here make sure to import it
you go to resource manager, then add a new resource with the + button, add a script file, find your script in that menu. then do the above.
for charecter scripts you then have one more step, find the charecter you plan on having that script run on and select it, in the sidebar look for "scripts" click the [...], then add your script to the charecter.