scorealign depends on portsmf, another component of the portmedia project. As such, you should install portsmf before beginning the installation of scorealign. This will also make sure you have all the required software already installed.
Instructions for installing portsmf can be found here.
Click Start > Run..., type cmd, and click OK. Navigate to the portmedia directory you made during the portsmf installation and type the following command:
svn co https://portmedia.svn.sourceforge.net/svnroot/portmedia/scorealign/trunk scorealign
This creates a folder called scorealign inside portmedia, then fills the port with the appropriate files.
You now have the files necessary to build scorealign.
Navigate to the portmedia directory you made during the portsmf installation. Inside this folder, create a subfolder called scorealign.
Right-click anywhere inside the portmedia folder and select TortoiseSVN > Repo-browser.
In the URL box that appears, type:
https://portmedia.svn.sourceforge.net/svnroot/portmedia/scorealign/trunk
The Repository Browser window appears. Right-click the folder called trunk and select Checkout....
In the Checkout window that appears, set the checkout directory to the scorealign folder you made above and click OK.
Once the files finish transferring, click OK, then click OK again to close the Repository Browser window.
You now have the files necessary to build scorealign.
Start Microsoft Visual C++, then click File > Open > Project/Solution.... Navigate to the scorealign folder and select scorealign.sln.
Click Build > Build Solution. The build should succeed.
Further documentation, as well as important information on how to use scorealign, is available in README.txt.