The rule is simple; you win if you capture the opponent king.
It is not necessary to find a person who plays the game with you when you want to play Shogi. You can enjoy it even when you are alone since your computer can be a good player. What more, you can choose the level of the computer according to your level.
I have learned a lot about how to win Shogi by watching YouTube posted by Tetsuya Fujimori, one of the professional Shogi players. His comments are so amazing, helping lots of people to improve their Shogi skills. The channel is available at https://www.youtube.com/channel/UC9Ije5dQVFx9uTGddG_U5XA.