first you have to set the entity you want to pick to be able to be picked, using:
http://blitzbasic.com/b3ddocs/command.php?name=EntityPickMode&ref=3d_a-z
then you can use the pick commands, this is the camera pick command, which is quite often used with the mouse co-ords to pick an entity that the user has clicked on:
http://blitzbasic.com/b3ddocs/command.php?name=CameraPick
http://blitzbasic.com/b3ddocs/command.php?name=EntityPickMode&ref=3d_a-z
then you can use the pick commands, this is the camera pick command, which is quite often used with the mouse co-ords to pick an entity that the user has clicked on:
http://blitzbasic.com/b3ddocs/command.php?name=CameraPick