In case of Spoken Tutorial No. 10- Plugins please follow the step-by-step process for 3D visualization:

Open GIS >> click plugins >> Manage and install plugin>> Search for QuickOSM plugin in all section and install the plugin >> similarly Search for Qgis2threejs plugin in all section and install the plugin >> Click close after installing both plugins.

To open OpenStreetMap: In browser panel on left hand go to “XYZ tiles” double click on  OpenStreetMap>> zoom in to the desired location you want to work on (Carefully select the area since large area require more time for processing) 

Go to vector >> click QuickOSM >> open QuickOSM bar>> in Quick query section under the “key” section search for buildings (keep value field empty)>> Under the option “In” select “Canvas extent”>> On the bottom right click “run query” and wait for process to finish (Keep all the boxes check in OSM file section)

After finishing the process, you will get three vector file named building in layer section

Go to web >> select Qgis2threejs >> select Qgis2threejs exporter>> under polygon tick “building” box >> also under DEM tick “flat plane” box 

The preview picture will look like 2D plane to convert the plane into 3D plane do the following steps:

Double click on building in polygon section >> building-layer properties will open>> under type change “polygon” to “Extruded” (you can see the height option box emerge)>> click apply and ok (the preview image will convert from 2D plane to 3D plane in Preview panel)>> close the window

To export the image: Under Qgis2threejs exporter>> click on file >> select export to web >> Under output directory select the folder where you want to save file >> provide page title “name” >> Check boxes for "present the current preview" and "enable to run viewer run locally">> In template section select "3D viewer with dat-gui panel">> click Export and close the "export the web" window.

Go to the folder where you have saved the file open the web page link, the 3D image from open street map will appear on your web browser.