Macbook new user asks about his computer

hi there!

I have just bought a brand-new 13" Macbook Air and i must say i am very happy and delighted to be using it. i find it very easy to use compared to my old Windows 7 laptop but also very different. it has been less than 24 hours since using it and i want to ask questions regarding its uses and OS in general:

1. I want to download & install a third-party software on the internet. After downloading the software (like say a browser) you have to still go to Downloads then double-click the software icon in a window before it can actually be installed. and you still have to drag the icon to the dock on the bottom. is this correct? am i doing the procedure wrong?

2. I want to find a file from a folder (from a portable hard drive connected via USB) and print it on my Airprint-enabled HP Photosmart 5110 printer. i am using a third-party software like Open Office. Do i always need to "find" the .doc file (either via Finder or Open Office) after opening the file?

Under System Preference i seem to not able to add a printer. when i rung Apple i was told that perhaps initially i may need to use a USB connection in order to actually add the printer then i can make use of the wireless part of it. is this correct? again, am i doing this wrong?

Please help....

Thanks.