The right pointing arrow at the top of the sketch is the upload button as shown below.
Click this arrow and the sketch will be uploaded to the Arduino, if everything is working. Try it.
You will see some words go by at the bottom of the sketch and hopefully some lights flash on the Arduino. If you see the words, “Done Uploading” as shown below, it worked.
This will erase any previous sketches stored on the Arduino. If you get to this point, you are past 90% of the hurdles of using an Arduino.
Next comes making it do something using a sketch.