Another item that has recently appeared is by Mike Aiello, N2HTT which is a 3 band VFO using a si5351 and an Arduino.
You get a much better understanding of how to use an Arduino with an Si5351, and of course, programming, by looking over the code of indviduals who really know what they are doing.
I made up my own version of the VFO using the same ATMega 2560 board with an Adafruit OLED and one of Jason's original breakout boards. The code for Mike's VFO can be found on the link above. The original code was for a 2560 but later code will work with an UNO.