RuneScape 3 has changed how the layout is completely, and many players have either learned to cope with it or given up altogether. This guide will detail how to return to a layout very similar to RuneScape before the interface update.
Look for a series of buttons. They will probably be on the left hand side. Find one shaped like a gear, and click it. This one is called "settings" though all you see is a tan gear in a brown background. Click straight on the gear. A couple options slide out, ignore them and click on the main button. You should have a popup open called "options menu."
In the menu, a little more than halfway down, it says "quick load layout" and right below it a dropdown menu. Click on the arrow to the right of the drop down menu (it will probably say something like "rs3 default" as the current selection) and select "old school." "Classic" and "retro" are options but generally are not as similar to RuneScape 2 as old school is.
Once you select it, the layout will revert to close to what it used to be like. You can then tweak a few things around as needed then save it as a preset in case you ever need to quickly reload it again.
You now can play RuneScape 3 in a layout very similar to what you are used to playing it in.