1. for the trackpad, click on the system preferences icon, or goto apple menu>system preferences, in the mouse and keyboard section (click the icon), select trackpad, and you will see a setting there that will enable that
2. goto system preferences, then goto the accounts icon (two black people), click the lock in the lower left corner if it is locked, enter your password, then click "ok"
after that, click your username in the left panel, and you will see a field where you can enter a different username