Chris, Cassie's suggestion to use the compendium's drag-and-drop ability is helpful, but if you need to manually edit a proficiency, it is possible. In the screenshot you posted, on the "Proficiency" line, where there's grey text that says "Elven, Dwarven, and Common," you can type the name of the proficiency. It will show up in the little grey box when you're done, and you can then click the little gear to stop editing the proficiency. If you want the proficiency to roll using a stat, like a skill, put it in the Tool Proficiencies & Custom Skills box. You can select a stat and bonus there-- you can even set a "Query" stat, which will pop up every time you roll that proficiency to ask which stat you're using (this is useful for certain tools, like Thieves Tools, which use variable stats based on what you're doing). To set up expertise and jack of all trades, you'll want to go to the sheet's settings (gear icon in the top right corner of the sheet) where you can manually select expertise, check the Jack of All Trades box, or add a flat bonus (such as you might gain from a feat). If you're manually adding the proficiency and you want your weapon proficiency to also give you an attack roll, you'll want to also add it to the "Attacks & Spellcasting" box.
