Pictures is indeed something most people are confused with at first, so I’ll quote what I mentioned before here:
As for some of your other questions, it’s not that hard. Just select the part of the text you want to make bold/recursive/underlined/larger and use the options in the bar above the text field (which can also be seen in the last picture above). Basically the same as regular MS Word.
If you hover over the other icons on this bar you can see what they are in their plain-text as well. Like the “Insert User Link”, where you can search for a user to tag (although you already did that in your question above with mine). Most of them are pretty self-explanatory.
The only semi-difficult thing is posting multiple quotes / parts of a quote, and text in between. In which case I switch to the BBCode part at the bottom to insert new-lines between the different quote-blocks, or to insert multiple quote-blocks. The BBCode part is the code behind the rich text field. I also use that part to insert spoilers usually, because I personally find it easier. But you can also just click the Spoiler-button on the bar (the last icon of the smiley with a finger before his mouth).
You’ll get used to it pretty fast. 
Welcome to the forum!
Greetz,
Quuador