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

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

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

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

Step 4: Select the type of card you want to addYou'll be presented with a variety of card options to choose from, including video or playlist cards, channel cards, and external link cards. Select the type of card you want to add.

Step 5: Enter the information for the cardOnce you've selected the type of card, you'll be prompted to enter the information for the card. This could be the video or playlist you want to promote, the channel you want to link to, or the external link you want to add.

Step 6: Preview the cardOnce you've entered the information for the card, you'll be able to preview the card to ensure that everything looks correct.

Step 7: Publish the cardOnce you're satisfied with the card, click on the "Publish" button to add the card to your video.

Note: You can add up to five cards per video and you can also schedule your cards to appear at specific times during the video. Also, Keep in mind that cards are only available on desktops and mobile devices, not on TVs or gaming consoles.

By following these steps, you can easily add cards to your YouTube videos. This can be a great way to promote other videos, playlists, and even external links within your own videos, and increase engagement, views and subscribers. Remember to use cards strategically, in order to drive more views and engagement, and grow your channel.