1.右键游戏库中的该游戏，选择“管理”——“控制器配置”
2.选择右侧的ABXY键区域，分别将A、B键自定义为键盘的空格、鼠标右键

也可以将其它按键自定义为游戏支持的快捷键，我知道的快捷键有，r：地图切换行走、跑步；战斗中重复上回合行动。Q：战斗时逃跑。F：自动使用最厉害的仙术。Esc:进入菜单界面。

Step 1: Right click the title of this game in your library, select "manage"——“configuration".
Step 2: Click ABXY on the pop-up window, set Button A as space, and Button B as right click.

You may also wanna set other buttons as some useful shortcuts build in this game, here are some examples.
R: repeat last turn's action.
Q: run away when in a battle.
F: use the most powerful skill automatically.