the easiest way is to just drag the amiibo.bin file on to the amiibo_sn.py file inside the folder provided by the OP.
if you cant do that then try this, i never really used python before so if my way is not the most efficient then my apologies.
try opening cmd and typing "cd ["amiibo_sn_changer" folder path]" then press enter. since i just have the folder on my desktop it looks like this "cd C:/Users/my user/Desktop/Amiibo_SN_Changer"
after that just type in "amiibo_sn.py [path/of/amiibo.bin]" hit enter and you will be asked to select how many copies you would want to make if you are using V2 of the program linked above. since i keep my amiibo on a folder in my desktop mines looks like this "amiibo_sn.py C:/Users/my user/Desktop/zelda amiibos/BotW guardian.bin"
although i would suggest trying to drag the amiibo.bin on to "amiibo_sn.py", i hope this helps if nothing else was working for you.