Insert the chuck diagonally from the side of the nut with the smallest oval diameter. Gently push the chuck to make the chuck fully enter the inside of the oval. Disassembly is the same step.
Priority is to install the chuck into the nut without falling, and place it in the tool holder to tighten the nut. The chuck is a spring chuck, the tighter you tighten, the greater the clamping strength. There may be some delays due to flight, holiday, weather, local post, local natural disaster impact. It must also be in the original packaging.