Visit MM Hamsoft page: http://hamsoft.ca/pages/mmsstv.php
Click on the MMSSTV113A.exe link as highlighted above, the file should automatically start to download.
The file is saved to the downloads folder, or can be seen at the bottom of your browser window.
Double click on the file to start the install.
Enter your call sign or name, this is only used when transmitting.
Click on option, then check sound input, is set to Virtual audio cable.
You can now open a web browser to websdr or sdr.hu locate a sdr receiver and tune to 14.230 (USB) SSTV on HF or for the International space station 145.800 wide FM
Good luck and please do share your pictures with us.