Adding elements like door and windows is easily facilitated by either creating or importing components into your SketchUp model. We show you how in our SketchUp training courses.
You can either create the door from scratch using the Rectangle, Offset, and Push/Pull tools. Then adding materials from the Materials panel. Or you can copy a door from another model and rescale it to fit your doorway. First open the other model and select the door with the Selection tool. Then go to the Edit drop-down menu and choose Copy, or type Control + C (Mac: Command + C). Next reopen your new model and go to Edit > Paste, or Control + V (Mac: Command + V).
We would then place the door anywhere in the model, preferably on the ground plane near its destination. Then move it into place with the Move tool (M), rotate it with the Rotate tool (Q), and scale it with the Scale tool (S).
Alternatively we can download a door from the 3D Warehouse, which is a repository of models that other users have created and uploaded. Go to Window > Components and click on the drop-down arrow. Choose Architecture or Construction and select a door component from the list. It will open in a larger window, allowing you to inspect the file’s size and details. If it’s not too large a file, and you are happy with the appearance of the door click the Download button. It takes only a few seconds to download into your model and is free of charge.
You can also create collections of your own favourite components via Window > Components. Click on the arrow button to the right of the search field and choose Create a Local Collection. Save it to your desktop or another location. Choose Make New Collection and name it. Then to save a component to this new collection right-click on the object and select Make Component. Then Save As and it’ll save it to your collection.
Many useful tips and techniques can be found at the SketchUp website. And see many examples of our own clients’ work on our Facebook page.
Other related SketchUp Blog Posts:

• SketchUp background
• SketchUp introduction
• SketchUp modeling
• SketchUp contours
• SketchUp workspace