ZModeler, like most of windows software, has a workspace area, menu, toolbars, some dockers and it's specific commands bar. Workspace area is split to views (by default, there are four views) where you can observe the scene from different angles. View with a solid boundary is an "active" view and you can navigate in it or apply tools. To activate any view, click anywhere in this view. In the beginning I strongly recommend to turn off View\All Views Active option in main menu. When you learn ZModeler more, you can enable this option so you don't need to click in view to activate it.
Main menu, like in most of the programs, contains commands and configuration options. Most of these tools are rarely used, since it takes some time to reach certain branch if there are pop-up branches. The tools you need most often are in toolbars - it's way easier to click on single button than to dig in menus. Of cause there are much more tools than toolbar can fit and software developers use thir own uproaches to lay more tools in toolbars (shelfes of bars, scrolling bars, drop-down buttons and so on). In ZModeler a Commands bar is used instead. This is a sort of vertical menu where items are stacked and can be achieved very easily. Even more, some tools have options boxes in commands bar. Image on the left shows a Copy tool selected. This tool is under Local Axes... branch and it's in a run under Display branch. All in one, Display...\Local Axes...\Copy tool is selected. Notice small pushed rectangle on the right of "Local Axes" - this is an "options box" (or "advanced settings box") show/hide button. On the image, certain options are set for "Local Axes" branch - these options are common for certain tools in this branch (Center to Object, Copy, Reset To World, Reset to Parent). To select a desired tool in commands bar, simply click on according labels "Display..." then "Local Axes..." and then "Copy". Labels ending with period "..." simply means that they are brachens and contain some tools under.
We shall now create simple Box. Click on a small down-arrow near Cone icon in
toolbar. A drop-down menu will appear where you should select "Box" icon. Once
selected, it will replace Cone icon in toolbar - Push this button and you are
ready to create a box: Click somewhere
in an active view (e.g. in Front view) and move mouse aside a little. A dashed rectange
will be drawn. Click once (you have specified the base of the box) and drag mouse
aside - a solid red rectangle will be drawn and a dashed line - they are the base
and a height of the box. Image below shows how it should look. If something goes
wrong, you can right-click to cancel creation of box and start again.
Click once again to create the box. A dialog box will popup - click OK there, since we don't need to change any properties currently. A box will be created in the scene and you can see it in all views. Push "Box" button in toolbar so it's no longer pressed (and "Box primitive" creation tool is no longer active). Your next step is to get used how to manipulate views to observe scene objects.