How Can I Learn to Explain Things Clearly and Confidently on the Spot?

There was a situation in my office where a leadership person walked in all of sudden and I had to explain him the kind of work our team was doing. I spent a minute in explaining it poorly. I was not organised and it was all over the place.

Thankfully a colleague who works closely with us and is part of the consulting team how deal regularly with clients, was able to beautifully put together the work done by our team. How do I develop expertise and my language skills and organise my thoughts like my colleague did, on the spot? It's not specifically to explain the work we are doing, but how do I develop to skills to explain anything clearly and confidently in an organised way. I don't even know how to think in organised way so as to explain. I just speak whatever comes to my mind on the spot.