Ryan wants to know how would he know if his computer had been hacked. Leo says that he can always scan his computer with antivirus software and with Microsoft's Malicious Software Removal Tool. In many cases, hackers are getting around that by moving their malware into routers and other "internet of things" devices. This is why updating the router's firmware is vital.
There are also other ways to find out. Unusual use of bandwidth is a clue. Popups he doesn't expect or recognize are indicators. Ryan should check out NMap, Wire Shark, and Microsoft SysInternals. A good firewall will also help. There's plenty of sophisticated tools, but they're sophisticated to use as well. This is ideal if he wants to get into IT security. Ryan should also keep his devices modern and up to date. Another is WhoIsOnMyWifi.com, but upon further research, Leo doesn't recommend that.