Inline text and image editing is done in the front-end editor of the website.
How you log in on the front-end can be found in the manual about logging in.
With short text we mean a shorter text of a maximum of 1 or 2 sentences, where the formatting of the text is always uniform.
Double click on the text you want to edit. A gray bar will appear above the text (see image on the right). You can now edit the text. There is a seperate manual on working with this text editor.
This is usually a longer text where the style of the text can vary and completely different elements can be added, such as Youtube videos and images. Most texts on the site that consist of more then one line are covered by formatted texts.
Double click on the text to edit it. A large gray bar appears above the text, as shown in the adjacent picture. There is a seperate manual on working with this text editor.
To see if an image can be edited, double click on the image. When a popup appears (like in the video on the right), the image can be edited.
Choose an image from the popup, or click on "Upload" to upload a whole new image. The popup will close itself, and within a few seconds the image will be replaced with the new image.
More about selecting images in the manual about selecting files.