Although the usual thing is to work with geometric type tools, sometimes we will need a more "human" or more "loose" type of stroke. For this we can use the pencil and calligraphic pen tools.
In the case of the pencil tool, its operation is very simple. You just have to click and, without releasing the mouse, move around our paper. The moment we release, the path is finished. If we get to the starting point, the path is closed, like a shape.
The most common is that we include a certain "smoothness" to the path, so that it does not reflect the trembling of the mouse. Smoothing around "40" is usually fine for a natural touch. If we go to higher indices, the path will look very little like what we draw. Here we see the same line with different smoothing:
In the tool's options band, to the right, in the "Shape" drop-down we can access other pencil styles. It may be interesting to try the one called "ellipse", which provides an irregular line.