The table of stats is in the upper-left section of the tab. The pool text field in the upper-right indicates how many points you have to spend. By default you can trade points on a point-for-point basis by lowering stats to raise the pool and then raise stats to lower the pool. By clicking on the Roll button you can re-randomize your stats. You can pick the randomization method by using the Options->Stat Roll Methods menu item. You can also purchase stats by clicking on the Purchase Mode checkbox. You can change the cost of stats by selecting the Options->Purchase Mode... menu item. When in Purchase Mode if you click on the Roll button all your stats will be set to 8. In Purchase or Roll Mode, if you click on the Zero button it will zero your pool. Typically for converting high-level characters you can click on the Unlimited Stats Pool button so you can change your stats at will, and once your stats are at your desired levels you can click on the Zero button. Characters who do not have a class yet are restricted to have stats no lower than the Stats Min field and no greater than the Stat Max field.
The middle section lists all your known Languages - either by means of race, class or skill. Some races and classes gain optional languages. These languages can be selected by clicking on the Choose button.
The bottom section lists all your special abilities. Currently it isn't possible to edit them directly, though this is in the plans.