Start DWG FastView for PC and open any drawing. On the right there is a Setting.
Click it and you will see:
Here you can change background color such as mine, which is black. Replace font style, keep font style of the drawing and remind me when font missing. Choose the open method when double-click a drawing in other places. For example, you received an drawing in Skype, double click it, you will be reminded to choose with which program to open it. If you do not want to open it with DWG FastView, you can untick here. Then next time when you open a drawing in other places, you can choose other pogram to open.
The last item is to set the size of the cross cursor. See screenshot below.