You can use keywords or more specific search terms to find boards and people to follow. For example, if you want to follow a board that posts pictures of kittens, you might type "kittens" into the search bar. You don't need to do this on desktop, since the "Filter" options are in the second row of tabs below the search bar. You'll select Boards to show only boards displaying your search term, or People to find Pinterest users to follow. On Android, tap Pinners to filter based on people. This option is below a board or person. Doing so will cause you to follow the board or person in question.
Open the Pinterest search bar. Search for a term related to your preferred content. Tap the filter icon right of the search bar. Select a filter. Tap or click Follow.