Hello,
In order to create the “About Brand” tab with HTML block, first of all, you need to show this tab in the single product page, go to Theme Settings -> Shop -> Brands -> enable the “Show tab with brand information” field.
https://monosnap.com/file/xLiwlaHuny5yNQGoPXaf9HCcif9qQq
After that, you need to create brands, in Product -> Attributes -> create for example the “Brand” attribute
https://monosnap.com/file/k9yM2EWaGnEco53CwZfwek5kips4II
In the “Brand” attribute, you can create different individual brands,
https://monosnap.com/file/rsOFsHHYDFFx5HElZyzd0zdyBv77C1
And in order to add a brand description, select some individual brand -> in the “Description” field enter the ID of your HTML block with a description.
https://monosnap.com/file/XV80aoaZQuL00jxHPIYqDiaf1Pc9E9
In order to indicate the brand of the product, go to Products -> select some product -> find the “product data” field -> select the “Attributes” tab -> and add the “Brands” attribute -> select individual brand for the product.
https://monosnap.com/file/R5vhT1Mjq80XQCJR22FTYGIbIfQzvp
https://monosnap.com/file/wV0eTqOKLfCPFkUnpQQX0kMX1jvOFE
Here you will see your final result
https://gyazo.com/ecb6629a7ac4c795ab4edf172a20ed73
Kind Regards