Ok so I think I finally figured this one out. This is for Windows Users as I don't own a Mac.
To have a database shared between two computers, placing it on a drive shared by two computers is recommended. Or a folder which both computers can access like a server.
First copy the DB files, the files are located natually under C:\Users\[username]\AppData\Roaming\XnViewMP
where the user name is the name of your pc. Be sure that you have "Show Hidden Folders" Turned on. This can be easily done through your folder options under the Control Panelhttp://imgur.com/hQ4XE1e
If the files aren't here, you might be able to find it by locating the INI file.
Open XnView. Now go under "Help > About" at the top. You will now see a new window.http://imgur.com/a/yeCRy
You do not need to mess with any INI settings.
Once you located the folder, You can copy the entire folder as you might want to save your settings across two computers as well if you are the same user. Otherwise the DB file will suffice.
Simply copy the folder and paste it to another file location which will be shared. Typically an external HardDrive or a server.
Under the Cog (gear) on the Main Toolbar or under Tools>Settings, Click down the side menu to Intergration, a new window should now appear. Under here click on the Paths tab at the top. Under "Other Settings" is where you can then use the DropDown menue to click on Custom which indicates a custom directory path. Here where you see the ... you can specify the exact path your new database directory is located.http://imgur.com/38UPDFk
When the db was originally created it might of had the DB referencing pictures on the drive, at least in my case since I wish to carry the pictures back and forth. The biggest issue is that on my main pc this drive was I:\\ and on my laptop this was D:\\ Which isn't good. To change this you will have to go under the control panel of your computer. Then locate administration tools. http://imgur.com/PeuORek
From there locate Computer Management http://imgur.com/aj0hmLE
Locate the external drive and then right click you should now see a new menu and click on "Change Drive Letter and Paths" Set this to which ever letter was the original path for your first PC. In my case this was I:\\
Now you should be all set.