Help with moving iweb website onto a computer that already has two active websites

My problem is not that I don't know where the files are stored to transfer my iweb website from one mac to another. My problem is that on the computer that I want to transfer it onto there is already 2 iweb sites running and active.

If there were no sites on this computer it would be no problem but I can't figure out how to integrate the new website with iweb since it already has 2 sites running on this computer without messing up the two sites that are active.

Any help would be appreciated.

The file that iWeb uses to contain your sites is called domain.sites2 in the folder user > library > application support > iWeb

Find the domain.sites2 file from your 'old' machine and copy it to a folder on your 'new' Mac (maybe a sub folder in your documents folder called site1 etc - doesn't matter too much).
For clarity, maybe copy your existing file to a folder in documents too, perhaps sites 2 and 3 etc

Here's the useful bit. Double click the sites2 file for the website you want to manage and iWeb will open it, allow you to edit etc. When you want to work on the other site double-click that one to open it.