The help section pretty much explains everything in their platform except technical and fundamentals, which you need to learn from other sources. Try to rephrase your query and be more specific, e.g. if you are looking for explanations just type the word you see on tws in the search box, instead of going directly into tws help section.
Basically, in order to buy and sell a security, you have to know the ticker symbol of it, type it in the blank showing in upper left corner on tws, choose sell(short)/buy(long), limited price, and quantity. Finally you press submit, the order is partially completed (called "live order"). Whether or not it will become your possession ("position") depends on the actual trading price in the market. One more thing: You’re free to choose “market price” for your order, it will be filled almost immediately if you do so. A limited price order will be filled quite late, but you can get a more desired price. I can't recall the abbreviations used for market and limit orders, but you can find all of them in help section.
