The commands of Forces are the following:
Del
It deletes all the forces applied on the selected nodes.
Mark
It activates a dialogue box where you can assign the forces applied to the selected node.
To activate the load you must put a check in the box near force's name.
The force applied to the node is visualised with a segment in the X or Y direction.
Info
It activates a pointer with a question mark: moving it on the screen and selecting a node, it appears a box with all the information about the forces applied to the selected nodes.