To create a brand new Media/Widget asset from scratch and add it to your guide:
While editing your guide, click on the Add / Reorder button at the bottom of the box where you want add this.
Select Media/Widget from the dropdown menu.
Give your asset a name in the Name field. This is how the asset will be identified in your assets library.
In the Embed Code field, enter or paste the HTML code you want to embed. Unless you're creating your own code from scratch, this will often be provided for you from the content provider or vendor.
Use the Position option to choose where the new asset should be inserted in the box. (Don't worry: you can always reorder it later.)
Click the Save button.
Assigning subject categories
If you would like to assign your asset to a subject category, click on the Subject Associations tab and select the subject(s) to assign. This will allow you to filter your assets by subject in your assets library.