How to restart my minecraft server and activate commands for myself such as /ban, etc?

If you are running a Minecraft server using Spigot (Works for 1.8 and above) or Bukkit (1.7.10 or below) you should have a plugins folder. Even if you do not install any plugins, you should have basic commands such as /ban, /kick, ect ingame and in the console - though you must be OP if you don't have any permission based plugins. Try /op (player name) in the console. If you do install some plugins, such as Group Manager, you can create groups and add permission nodes to each group. You can find a lot of more info out there for that topic. Hope this helped. Also for restarting the server, access your server console and type 'stop' and you can then start it back up.