Welcome to the community. 
A security program on your PC or network is likely interfering with WeMod.
See here for the steps to resolve it: I can’t Install WeMod / "There was a error installing the application" - #2 by Ravenfyre.
As a side note, please do not add unnecessary tags to your post, such as the free games tag, which I removed. It makes the community messy and causes users to take longer to find what they actually want through the tags.