You will need: (I've listed Adafruit items but you can get them almost anywhere)
10K contrast potentiometer
LCD (compatible with Hitachi HD44780 driver) + contrast pot
Rotary encoder with push-button switch
Adafruit Si5351 Breakout Board
I use clk0 for the vfo and clk2 for the bfo.
*Your LCD may have a current limiting resistor already installed between pin 15 and the back light, In that case, you can supply +5v to directly to pin 15.
Use this updated sketch and library from this page that will allow for IF offsets, X4 output or Direct Conversion receivers
If you've never used Arduino before go here to the Programming Electronics Academy and watch the first the first and second videos (watch the second one first!). It can't be stressed how important it is to do a proper install of the Arduino IDE(Integrated Developement Environment) so that your programs and your downloaded libraries stay separate from the location of the Arduino IDE and the libraries that are included with each new version of a new IDE download.