The club show it on a video
Shirts, boots, shorts, the armband and whatever is needed. Barça players don't need to care anymore for the clothes they will wear in a football match, as they used to do when they were young and had to prepare everything for their football matches.
This is how the first team kits are prepared on a matchday. The club show it in this video, where the fans can discover how the people in charge of it worked before the derby match between Espanyol and Barça at Cornella-Prat.