You can upload content directly from your device by going through any outlet that permits access to the Media Library (General Content, Image Gallery, Sectioned Content, Call to Action).
Let's use the Sectioned Content as an example.
Click on the Image icon to bring up the Media Library. Here, you can see all of the content you have uploaded as well as any folders you have organised for content.
When this window pops up, click the icon. Once this is done, another window will pop up.
Click the + icon then select your image. Once you have done that, hit "Upload Now." Scroll down to your image and click "Insert" and your image will now be in your Sectioned Content.