You can access the Asset management page by clicking on the Assets menu item.

Here you can see a list of all your uploaded assets, including a preview for images, file name, type, and url. You also have a filter option on the left hand side to quickly filter between images and videos. 

Click on New to create a new Asset record

In the new Asset form you can click on the Upload button to add your new Asset. Once uploaded the details of your asset will be saved in your workspace, if you didn’t provide a name for your asset the original file name will be used, but you can always change this by editing the File Name on your Asset record. Once saved you will be presented with the File Url you can use to deliver your asset as well as the API Id in the General section to query your asset using the API.