I am Vinod. I will try my best to help you resolve this issue.
It is very easy to add songs to the itunes. If you have a folder containing songs, just open itunes and drag that folder into itunes. If it is a song you need to add, just drag that song into itunes. Similarly, to transfer the songs from your wife's laptop, follow this procedure - Open itunes in your wife's laptop. I hope it is a windows computer. After opening itunes, click on the edit menu at the top (where it shows File, Edit, View, Controls etc). Click on Edit > Preferences > advanced tab. There, you will find the itunes media folder location. That is the location where the music is stored. Just navigate to that location and copy the folder containing the songs into an external hard drive or usb drive and copy it into somewhere in your computer. Then, drag that folder into your itunes.Let me know if you have any difficulty
But if you do the above steps, all the music will be in one library. If you want to keep your wife's library separate, it is better and less confusing to create a new user account in your computer. So if you wife wants to use the computer, she can log in to her user account and if you want to access your itunes, you can log in to your account. To create a user account, just go to the control panel and select the user accounts. Make sure you create an administrator account.
ok thanks for the info