When it comes to actually buying shares the page has terms I dont understand. I take it if I want to buy or sell shares then I enter the details in the Place buy order and Place sell order tabs. But what do the bid and ask tabs below it mean especially the Fill buttons I'm not sure what they are?
The Fill buttons pre-fill out the corresponding Buy and Sell sections.
If there is a line for someone selling (ASK) 5 at 2.... and you click the Fill button, your Buy window will fill in 5 at 2 for a total of 10. At which point you can click the Place Buy Order button if you wish.
It's OK to click the Fill buttons to see what they do (they won't process an order).