Drag a image over a placeholder, and then when prompted, select the option you want:

•Select Crop if the image is wider AND higher than the placeholder.
The placeholder will not change its dimensions. This is not available if the picture is smaller of the placeholder.

•Select Fit to fit one side of the image in the placeholder and to crop the other side.
The placeholder will not change its dimensions.

•Select Resize to fit one side of the image to the placeholder and to scale the image to fit the other side. The placeholder will not change its dimensions. Warning: this may lead to the distortion of the picture.