You will start your adventures in a small farm village called Greentree. You will have a tip box show up that explains you how to control your character. Simply use the W, S, Q, E keys to move, and A and D to rotate. You can adjust the keys in the Options-window.
To rotate your character around you can also use the mouse by keeping the right mouse button pressed and moving the mouse around. Mouse's scroll will adjust the zoom, and if you want to rotate around the character you can keep the middle mouse button/scroll pressed and move the mouse around.
Now walk to the chest in the room, click it to pick up your stuff and finally leave the room to begin your adventures.
Once you have arrived in the Greentree Inn you'll meet lots of people who you can talk to. Talking with NPCs is easy, just left click them when you're near them.
Start by talking with the Helper-NPC to learn some more about the game.
The game has several quickslot-sets which can contain both usable items and skills. Assigning of an item or a skill can be done by dragging item from inventory or a skill from the Skill-tab of Character Details-window into quickslot.
Clearing a quickslot can be done with Shift+Right Click at the slot.
In Gekkeiju Online™ almost everything can be Right Clicked with mouse to get more information. This includes items, skills, abilities etc. So always try Right Click when in doubt as it may offer you some quick information.
Next: Leveling up