Step 1: Open the browser (Google Chrome,Opera Mini,etc.) that you have installed in your computer.
Step 2: Type "download geogebra" on the search box,then click on the "search" option.
Step 3: Click on the link "Download GeoGebra Apps".
Step 4: Click on the "download" option situated below the box "GeoGebra Classic 5".
Step 5: Click on the "save" option.
After installing the geogebra software,you can run that to make and open the geogebra applets.