To resize them, go into Options > UI settings, and at the bottom there are sliders for the different elements (for panels and the chatbox, just drag at the top to move it and drag any edge or corner to resize it). The higher the number, the bigger it is on your UI and the more space it takes up. The smaller the number, the less space it takes, but the harder it is to see or click on. They are all defaulted to 1.00, and can go between 0.40 and 3.00. Adjust these until you feel comfortable with where they are and how big or small they are. Note: you may want to leave some space for plugins and such, if you plan on using any.