It is up to you if you want to use an ENB or not. If you already have a problem getting a high enough framerate, you should probably not use an ENB.
Download the latest version by clicking on the version number in the lower left side of the screen. This open a new page that has the download link on the bottom.
Open the downloaded archive and extract the files ‘d3d11.dll* and *d3dcompiler_46e.dll* to the main game folder.