Adding filters is as easy as clicking on the button, located at the top of the Asset View in the Content Browser. This will bring up the Filters List, with flyout submenus available in each category. Select each type of filter you want to add it to the Filter Bar, which is only visible when you have one or more active filters.
You may add as many filters to your current Asset View as you like. Filters are additive by nature, meaning that if you start by selecting the Static Mesh filter, you will only see Static Meshes. If you then select the Blueprint filter, you will see Static Meshes and Blueprints. Each filter you add increases the number of available asset types. Keep in mind that you can always see how many assets are currently visible in the lower-left corner of the Asset View.
You can add all filters under a given category of the filters list by selecting the category itself.