YouTube end screens are a powerful tool that can help you to promote other videos, playlists, and even external links at the end of your videos. Here's a step-by-step guide on how to add end screens to your YouTube videos:

Step 1: Sign in to your YouTube accountTo add end screens to your YouTube videos, you'll first need to sign in to your YouTube account.

Step 2: Select the video you want to add end screens toOnce you're signed in, go to your YouTube channel and select the video that you want to add end screens to.

Step 3: Click on the "Edit video" buttonOnce you've selected the video, click on the "Edit video" button located under the video.

Step 4: Click on the "End screen" tabOn the video editor page, you'll find an "End screen" tab, click on it.

Step 5: Select the element you want to addYou'll be presented with a variety of end screen elements to choose from, including video or playlist elements, channel elements, and external link elements. Select the element you want to add.

Step 6: Customize the elementOnce you've selected the element, you can customize the element by adding a title, image, and even a call-to-action.

Step 7: Preview the end screenOnce you've customized the end screen, you'll be able to preview the end screen to ensure that everything looks correct.

Step 8: Save the end screenOnce you're satisfied with the end screen, click on the "Save" button to add the end screen to your video.

Note: You can add up to four elements on your end screen, and you can also schedule the end screen to appear at a specific time during the video. Also, keep in mind that end screens are only available on desktops and mobile devices, not on TVs or gaming consoles.