You need to have a very large investment in steem to have a bot and then you have to know how to write one or borrow/steal someone elses code and run it yourself. then you need a server to run it 24/7. If you are not that technical and still wish to invest a large amount into steem you can also sell your Steem power to a vote bot, increasing the bots power and taking a share of the profits. Check out smartsteem.