For YouTube a link is all you want to put into the bot's message. Telegram will automatically show YouTube videos.
If you have a specific video file, you need to upload it to the web somewhere then you can include a video tag in the bot's message.
bot: Here is a video
Bot Libre will automatically convert the HTML video tag into a Telegram video message (same for image and audio).
For other types of files you need to include a link in the message, Bot Libre cannot send the file directly in the message.