How to Install WiFi.Udp.h

Please post your full sketch. If possible, you should always post code directly in the forum thread as text using code tags (</> button on the toolbar). This will make it easy for anyone to look at it, which will increase the likelihood of you getting help. If the sketch is longer than the forum will allow then it's OK to add it as an attachment. After clicking the "Reply" button, you will see an "Attachments and other settings" link.

Please always do an Auto Format (Tools > Auto Format in the Arduino IDE or Ctrl + B in the Arduino Web Editor) on your code before posting it. This will make it easier for you to spot bugs and make it easier for us to read.