When using images within your Markdown content, it is possible to specify the required size the image should be resized to by appending a query string to the file URL as follows:
The snippet above would resize
image.jpg to a width of 400 pixels and a height of 300 pixels.
The second option to resize images is to use the file manager. Just use the little dropdown of any image file and select
Copy Resized to open the resizing dialog.