hi guys I need your HELP! How I can get the passwords to enter a room???

Some rooms have passwords because the player hosting the room set the room to have a password. You're not supposed to know what the password is unless the host told you what the password is. i.e. the host is expecting certain other players to join and not someone he/she doesn't know.

If you see that every room has a password, you are encouraged to host your own online room. Make sure that no password is required if you want it to be open to everyone/anyone.

Thanks, but what did the "N" or "Y" means? Probably they are "Yes" and "No", but why? [I'm sorry. I'm Italian and I can't speak English very well...]

And how I can change my profile image??

Correct, Y and N means Yes and No, meaning "yes there is a password" and "there is no password" for the room.
This also applies to the room being locked or unlocked. If it's locked you can't enter the room (because there is a match currently being played in there), so you'd have to wait for it to be unlocked when the current match is finished.

You can change your profile image by clicking on "user control panel" on the top of this page. Then you click on "profile", followed by "edit avatar". While there, you can click on the button to chose a file straight from you computer (the image must be 180 pixels by 180 pixels or less. However, if you found an image online through google or whatever, you can copy the URL to the picture and paste it in the area that says "Link off-site". If you do this, you must define the dimensions of the image in the area below that section. Remember, the largest the image dimensions are allowed to be re 180 pixels by 180 pixels. Read the page for more details.

The game request the password also if there is "N". Should I leave empty?

leave it empty, yea

Ok, I'll try. T(h)anks.