The best way would be with a pressure brake bleeder.
If you do not have one of these available then thoroughly manually bleeding will work just as well.
I have attached below a description of the manual brake bleeding process.
There is also a guide for brake pedal goes to the floor in the link below:
Bleed the entire system until you have fresh clean fluid with no air at every corner.
If the problem persists make sure you have gone through the guide in the link.
Let us know is you have any further questions.
Monday, February 17th, 2020 AT 2:12 PM