Deep Spirits

[Sabina]

The Forum Help & How to already explains the basic principles of adding images to the forum.

However, it is possible that you run into a problem when using the Upload attachment feature to add an image to your post.
The image you want to upload cannot be wider than 575 pixels.
If you have a photo editing software, then changing the image proportions and downsizing an image to a width of 575 pixels is a piece of cake. However, if you are not familiar with this process and/or don't have any photo editing software installed, there is a handy online tool that you can use instead.

ResizeYourImage.com allows you to just that. Start by uploading your image, and then click the little "width" image above it. A popup box will open which allows you to enter the exact width you would like for your photograph.
When you are done, click the yellowish round button and you will be taken to a page where you can download your image, cut to length.

By the way, when you are uploading an avatar image, there are no such issues. You can even use gigantic images.. after they are uploaded, they will automatically be downsized to proper dimensions.