You can't keep it on top because then you couldn't work with other applications like Safari, which I will use as an example.
Take the open window of one application, click and hold and move the cursor so the window is in a position not covered up by the window of another application. Offset it from its present position. Another option is to move the cursor to the bottom right of your password application and make the window bigger than the Safari window. In either method, the idea is to get the window visible even when using Safari. You can then click on the window and it will come to the top. See the screen shot below.
The top window is where I am typing this reply. There is another window (black) to the left, which is another Safari window. The window at the top is the Mail application. The little portion of the window at the bottom is the Calendar application. To switch between the windows I can just click on Mail, for example, and it will appear on top.
Since you have only had your Mac two days, let me know if you understand this. If you do, then I'll type the Spaces option.
Don't want to create a 'fire hose' approach. It takes time to learn a new system. I got baffled tonight trying to work on a machine running 10.5.4 because it has been at least 4 years since I used that OS.
Glad to help.
Yes to your question above.
Let me correct myself first. Spaces is the old name for what are now called desktops.
The way I have my computer set up is with four desktops.The first desktop is Finder and where I open miscellaneous items. The second desktop holds Mail, Safari, and Calendar. The third desktop holds my financial stuff, and the fourth desktop is where I open Word and other Office applications. I like this setup because (to me) it is organized and I don't have all the applications on top of each other. On the desktops, the open applications are staggered like the screen shot above.
Three ways to navigate between desktops:
1. Hold down the control key and use the left/right arrows to change desktops.
2. Open Mission Control and click on the desktop you want to have showing.
3. Go to System Preferences/Keyboard, unlock if locked and select Mission Control. Check the boxes "Switch to Desktop X"
Open the application Mission Control and you can see the desktops you now have.
If this sort of set up interests you, post back and I'll do my best to try to get you set up.