At the end of the page, in the "Tools & Software" part you will find "Resistor Calculator for Op Amp Gain and Zero Shift"
Then click on: RESISTOR-CALC
Enter your input voltage scale: 0.4V to 2V (see below)
Enter your desired output scale: 0 to 4V
Click the calculate button and follow the instructions... ... done
Use a 100R resistor to convert the 4 to 20mA to 0.4 to 2V then an opamp to amplify it from 0 to 4V.