1) I assume you have the Virtual Sailor running inside "c:\program
2) Take the add-on file for example victory.exe and copy it into this directory.
3) Run the victory.exe by double-clicking it.
4) It should open a small dialog and on it you will see a button called Unzip.
5) press the Unzip button and let the file unzip itself into the program.
6) Run the program and from it select the new scenery or boat.
7) now sail and explore the scenery or boat.
8) Repeat the process for every add-on file you download.
To install add-ons in the form of zip files, found on the library, do the following:
1) Select the add-on from the Library page, press the zip file link to download
2) Create a new directory somewhere on your computer and put this file inside.
3) Using Winzip or WinRAR click the right mouse button upon this zip file and select extract to...
This will create a directory by that name inside this new directory you created.
4) Now explore this directory, it may contain panels, weapons, instruments and sometimes the name of the boat itself.
Select the panel, instruments, weapons, boats, directories and right click with your mouse, select "copy".
5) Now, browse to the directory your program is installed, typically "c:\program files\virtual sailor"
Then right click your mouse button there and slect "paste", this will transfer the directories here,
when you have also a directory by the name of the boat itself, proceed below to copy into the boats directory.
6) Browse to the boats directory of the program and paste this directory here.
7) Now, start the program and explore the add-on you have just added.