Outlining the Mouse
We need to outline the mouse's contour, ears and eyes with a pencil - but the image is very visually busy, and makes it difficult. Let's insert a semitransparent rectangle above the picture's layer, to make the background pattern less busy. Create a layer "gray", to position it above the picture but below the outline layer go to LAYER->LOWER LAYER while "gray" is selected.There is a lock icon to the left of the layer list - pressing it prevents the selected layer from being modified. Select "picture" and press the lock icon, for now we don't want it to move around.
Now we need to actually put a semitransparent gray rectangle on the "gray" layer to dull down the image. Go to the vertical icon bar on the left, it contains different drawing tools. Select the blue rectangle icon and create a rectangle on the "gray" layer that covers the mouse picture. The rectangle's fill is not transparent gray. Let's change the fill colour and get rid of the rectangle's outline by going to the "Fill and Stroke" dialog at the top icon bar, the icon looks like a gray circular button.
The "Fill and Stroke" dialogue lets you change the fill colour of shapes and their outline. You can also change the style of lines you draw (paths). A menu will pop up, go to the "Fill" tab, choose "Flat Colour" and choose a gray colour on the colour wheel. At the bottom of the menu you will see an opacity slider, make move the slider towards the lighter part to make the rectangle transparent. Go to the "Stroke" tab and select the "X" to get rid of the square's outline.
Go to the layer list, select "gray" and lock it by clicking the lock icon to the left of the list. Then select the (topmost) "outline" layer. To start outlining the mouse select the "Freehand Lines" tool from the vertical icon bar.
Outline the mouse using this tool.
Don't worry if the outline is not perfect.
Select all the separate lines using the arrow tool which is the top icon on the vertical bar. Your screen should look like the above picture. Press CTRL-L several times, this will smooth out ("simplify") your outline. To tweak parts of the outline double click the line in question, small squares will appear (these are the parts of your "path", your line). Stretch them to fit the line around the mouse's features. Below is the simplified mouse outline.
