You need a Windows Operating System, which PCs have, but Mac does not.
The designs at this site are .pes, but occasionally another format is used by the designer.
The designs are in a zipped file and have to be extracted.
Before downloading, create a new folder and name it "embroidery", or some variation so you can easily access the folder.
Choose the file (design)) you want to download and save to the folder you created.
Open the folder and highlight the file you want to open. A small window will come up on the screen and if you choose open or extract the file will open.
If you need a different format, go to Download Designs and select Pulse Ambassador. This is a free software program that you can download and use for viewing as well as format conversion.