The toolbar at the bottom of the viewer groups the navigation tools: orbit (rotate around the model), pan, zoom, fit to the whole model, and the navigation cube at the top right to choose a face or an isometric view.

“First person” mode (person icon) puts you at eye level inside the building: move with the arrow keys or the W/A/S/D keys and look around with the mouse. Hold Shift to go faster.

The “Rectangle selection (multiple elements)” tool, added by FunBIM in the same toolbar, selects in one stroke all the objects inside a frame — handy for isolating an area or creating several progress items at once.