Beco Gemini instructions can be found here: https://becobabycarrier.co.uk/pages/beco-gemini-instructions
A photo guide to putting on a waistbanded carrier with crossed straps: https://www.carryingmatters.co.uk/sleepy-nico-front-carry-with-cross-straps-photo-tutorial/
A guide to adjusting the carrier if it is too tall (the top of the carrier should sit in the nape of the baby's neck): https://www.carryingmatters.co.uk/raising-baby-up-panel-carrier-photo-tutorial/
This hire carrier has "quick click" buckles.