Practice. Look for opportunities to give talks and make a talk complete w/ slides about something you did. Give the same talk or almost the same talk at a few different places. Write a blog post about it.
This is the approach to take. Getting better at conversations, impromptu ones in a low risk environment is going to help. Go to meetups or the like and talk to others about hobbies you have an interest in. Maybe its board games, go to a board game shop and chat with people. There are clubs that do this - Toastmasters I believe is the name of one from some time ago, although I haven't heard them mentioned post-pandemic.