In Cura's Dual Extrusion setting, turn on the prime tower.

Set up as shown in the image.

Set the prime tower in a rear-central location on the bed. This is so the PTFE tube isn't being pushed one way or the other which could prevent switching.

Retraction between switches is important, we've set the default value to 6mm but you may need less or more here depending on the length of your bowden tube. When working with bowden extruders it's best to start with a small value here and work up, too high a value from the beginning can cause the hotend to clog.