Welcome to the game!
I'm going to assume you left the spawning area and entered the wilderness or chose a charterstone. Since you didn't know how to put items in your inventory you probably skipped picking up the freebies you get when you spawn. That is okay, however you will experience a difficult start up.
To pick up items you simply have to right click on them in the game world. They will show up in your inventory. To equip items to your character or change your look. Go to your inventory(TAB) and open up your equipment screen(ctrl-E). Click on an equip-able item then click on your displayed character.
Seeing as you are new I recommend that you read this forum post which will guide you and familiarize you with the mechanics of the game.
viewtopic.php?f=2&t=3196Good luck!