Install an axle support on to the two posts on the face of the carriage as shown in the first photograph.

Fit a 3" axle into the axle groove in the mount. Ensure that it's centered on the carriage.

Using two #4, 1/2" machine screws and two #4 washers, fix the axle and axle mount in place as shown in the second photo.

You're done! Re-install the delta arms - they go back on just as they did the old carriages. You'll need to change your Horizontal Radius in order to recalibrate your printer properly.