Use Modify|Add to schedule files or directories for addition to SVN control.
In case of directories you have the option to Recurse into subdirectories, which, when selected, causes all subdirectories and files from subdirectories to be added as well.
When a file is added, SmartSVN automatically applies certain properties to the file. Most important is the automatic detection of the file's MIME-Type, which can basically be text or binary. Further property defaults can be specified in the project settings .
Automatic detection can be overridden by the Binary Files project settings (see Binary Files).