The installation process is identical to the standard version, but with one extra checkbox.
The Addon Support version is often unsigned. Your antivirus might flag it, but it is safe when downloaded from reshade.me .
Your shaders or preset files may be in the wrong place. The ReShade installer creates a reshade-shaders folder. Make sure any custom shaders you download are placed in the correct Shaders and Textures subfolders within that directory.