Well, once you downloaded a preset you can just open it by double clicking it. Or if you open the BTT window, through the Preset Button in the top right corner you find the possibility to open an existing preset.
If you already know what you want to achieve, the easiest is to create your own buttons and giving them the function you want (BTT offers a lot of them). Just start ahead and discover it, it's quite easily once you ,add the first steps
If you rather look for something prepared, check out these presets:
