Start with your own backgarden where you will find all manner of visitors such as birds, squirrels, hedgehog, fox - I bet there are all manner of creatures if you look closely enough.
You don't have a garden! What about your local park or grassland or even a farm. What about small creatures - insects, moths, butterfly's - the list can be endless.
Hey, don't forget pets, yours or your neighbour or friends - I bet they would love to have a nice portrait of their pet dog/cat/rabbit.
And don't think you need specialist equipment either, start out with what you have, you can get great images with just your mobile phone! Just go out and take some photographs, you will be glad you did!