This assumes you have Subversion installed on your local PC. These examples are based on Linux.
The svn checkout (or svn co for short) command can be used to check out files from one of your Subversion repositories. For example, let's say http://example.com/svn/repo/testing is a repository of files being version controlled by Subversion. You can check out the repository.
svn co http://example.com/svn/repo/testing
When you do not provide a username and password, you will be prompted to authenticate. The --username and --password options can be used on the command line to authenticate. If you don't know the username and password, refer to configuring basic authentication for Subversion.
svn co http://example.com/svn/repo/testing --username=johndoe --password=secret
Be aware that if there is an exclamation point in the password, the exclamation point will need to be escaped.
svn co http://example.com/svn/repo/testing --username=johndoe --password=secret\!
When you do not specify the target directory, the working copy of the repository will be created in your present working directory. In this example, a directory named "testing" will be created in the present working directory.
Often, it is preferred to define the name of the directory on your local PC that will contain the working copy of the respository.
svn co http://example.com/svn/repo/testing /tmp/SVN
You can then modify the files locally. Once you are ready to commit the updated file back into the master Subversion repository, you would svn commit the file.