how to make trailer

so ive finished my project and i want to make trailer but IDK/im not sure how to make it

ive found a tutorial but i dont know if its works or not (how to export the video/how to add music to it)

and also i wanna add music to my trailer and IDK this one either

if you know any tutorial please send the link/or… idk please help:(
THANKS

You can record your video after preparing and coding your trailer, and then edit it in an editing program!