I keep seeing all these posts that someone can hack my wallet. First I did not think that this could be done? If it can be done, how can I prevent it from happening? Does my wallet need to be online in order for them to be able to hack it or can they still hack a paper wallet?
It is possible that someone can just guess or brute force your private key. The chance however is so small you might as well call it impossible. Its as likely as someone winning the lottery several times in a row and will for all we know never happen as long as the sun is still burning.
Other than that it mostly depends on the way you use your machine. As AllInCrypto said if the machine that you use to control your wallet is infected by malware, its easy for the attacker to spend your coins. Its however not "easy" to infect a modern, well updated system, unless you do something to help the malware. Commonly bitcoin related malware will require you to execute it yourself, so be careful what you download and use.