Art is supposed to speak to you. Many factors influence how people understand and interpret art. These include their state of mind when interacting with art, cultural beliefs, and previous interactions with art pieces.
To understand a work of art, you must be in the right mind frame. Take your time to examine it and let it get to you. If you are having trouble understanding it, you should consider taking a break and coming back when you feel your mind is fresher and able to take in new information.
You should also consider checking out previous works by the artist to give you context on the kind of art pieces they have done in the past. This will help you understand the genre and possible meaning of the work you are currently looking for. Doing research on the artist also helps to give you context on their backgrounds, and this can add further insights into the art they do. Do not be afraid of interpreting art the way you feel. There is never one wrong or right answer. It all depends on how the piece of art has touched you.