Captions provide a text description of the audio and sound of a video or multimedia content. This users engage with the content even if they aren't able or don't want to use the sound portion.
<title>attribute to the embed code if video is using an iFrame
If your team is new to captioning find out if some other group in your organization creating video content, like your university's TV channel. Reach out to them to ask if they have experience captioning and what tools they're using.
Talk to your LibGuides authors to identify who's using or creating a lot of video content. Get them involved in developing best practice around captioning workflows and training. If that training can be offered more widely than just LibGuides authors the better to help create cross-departmental buy-in and understanding about accessibility.