You can select a node by clicking on it. You can use the Ctrl key while clicking to select multiple nodes. If a selected node is clicked with the Ctrl key it will be de-selected, as is typical with virtually all computer systems.
You can also select nodes by dragging around them. First, select the object that you would like to edit. Then drag around the nodes you want. When you release your mouse button, the nodes inside the area you dragged will be selected.
You can also operate on holes, carving lines and breaklines in this manner – drag around the nodes you wish to adjust.