What you need to Open and Edit the Files.
The vector files come in standard EPS format, the standard and the most usable file format for all vectors. However, you need to have a vector editor software such as Corel Draw, Adobe Illustrator, Inkscape etc. to be able to view and modify the vector files for your own desired use. Many of these software are available for a free trial of 30-60 days, there are also lots of Open Source Software that are absolutely free yet are capable of producing very high end products.
Remember that you are only buying the licence to use the image, these vectors are not to be under any circumstance be resold by the customer to another customer, we will take appropriate legal procedures against any individual or company we shall find reselling our products online.