How do I create a custom preset?

You can create a new preset by clicking on the + sign in the upper right side of the Presets Panel or copy settings by right-clicking an images and selecting Develop Settings > Copy. When creating a new preset, make sure to name it something unique as to not overwrite one of the VSCO Film presets.  If you copy the settings, you can then select all of the photos you want to apply it to and then right-click and select Develop Settings > Paste.  

Below is a screen shot of what you want checked/unchecked (you may or may not want Lens Vignetting checked).