If you have Trust Level 2 (or higher) you can embed YouTube videos into your posts just by pasting the URL of the video into the body of your post.
More about Trust Levels, and how to obtain / maintain them, can be found in the stickied thread at the top of the forum…
However, there’s been recent threads discussing whether the stated requirements are still the case or not as a number of us have lost our Trust Level 3 whilst seeming to still satisfy the requirements…