Okay. So you've Installed Blender and BlenderBIM.
Luckily you have the latest version of BlenderBIM. If not, you can find a video explaining how to upgrade BlenderBIM.
Depending on when you've last upgraded BlenderBIM, you may notice constant UI changes. The point is not to make you more confused, but rather to unify the User interface and make it more intuitive by separating Blender from BlenderBIM functionality. Some panels haven't moved, but the everything is meant to be grouped under the Scene Panels, and you can now switch tabs to access different functionality.
Before going any further, we'll tweek the BIM workspace a bit.
We'll change the Viewport color. I want it white, but you do as you please. We'll go to the top right corner, and click on the Viewport shading and set it as " Material Shading".
The go the the World Properties in the Properties panel, and change the color to white.
We'll go to the top right corner, and click on the magnet icon. We'll set it to "Vertex", "Edge", "Edge Center, "Edge perpendicular".
Shift + A > Add > Mesh > Plane. We'll hit F2 and rename it to "Reference Plane". We'll hit Tab, scale it byt 0.5, and hit Tab again. We'll hit G and move it by 0.5 in the X axis, and repeat the process for the Y axis. We now have a 1m x 1m plane.
To add an origin point, we'll hit shift + A > Add Empty > Arrows. We'll hit F2 and rename it to "False Orirgin XYZ".
File > Defaults > Save Startup File.