From Online Manual
Thank you for deciding to convert to, or at least test the conversion to SMF. Before you get started, please remember that the conversion will not overwrite or change your existing forum, and that there is a place for help at www.simplemachines.org if you run into any problems at all. There is a separate help board - Category:Converters and Importers where you can ask for help with converting to SMF. Next: What's required to run SMF?
The first thing you need to do, before you can convert, is upload all of the files in the installation package found on the downloads page to your server in, preferably, a directory other than your current software. You can upload it to any directory accessible by URL. If you're not sure where to put it, a directory named "forum" or "smf" is a good choice. You may wish to make sure that all of the folders were uploaded, such as Themes/default/languages, because some FTP clients have been known to drop files.
Note: The converter will not work unless SMF has access to the database that the forum you're converting from is on. For best results, you should install SMF on the same database as the forum you're converting from. If this is not possible, you will need to make sure that the database user account being used for SMF has access to the other forum's database. If you are not sure how to do this, please ask on the forum and someone should be able to assist you.
Category:A complete installation guide is also available. Converting from your current software
After you have finished with the installer (it should walk you through the rest of the process) and deleted the install.php file, you're ready to get the conversion process going. Be warned, however, that the process can take some time for larger forums, because it has been engineered not to disrupt the server's normal operations.
To begin, download the converter you want from the download page. If there is no converter available for the software or version you're using or the converter on the downloads page doesn't work, please check the Category:Converters and Importers board for more information and links to updated converters that may work. The converters can be found as a sticky topic inside of the child boards for the forum you are converting from. Otherwise, download the files (for example, it might be yoursoftware_to_smf.sql and convert.php) and upload it to the same folder as SMF. Please note that the converter will not delete or edit any data in the original location, it will simply copy it into the new format.
Once that's done, use your browser to go to http://www.yourdomain.tld/forum/convert.php, where www.yourdomain.tld/forum is the URL to where you put SMF. You should be presented with two boxes - one for the path to SMF, which should already be correct, and another for your software. The converters will detect if the path is correct for you, so if it takes a few tries, don't worry. You will also see a box for the current password - this should be the password for the database account you installed SMF with.
After you hit continue, the conversion process will begin. Depending on the size of your forum, it may take quite some time, but it will continue for you automatically, the status bar will appear to keep you informed of progress. Near the end, you may be prompted to specify whether you wish for some extra features to be converted, but that is very converter-specific.
Finishing everything up
From this point, the converter should walk you through everything. If you have any trouble please visit the support forum.
Please remember to delete the converter and install.php files after the process is complete. If you do not delete them, it is possible that someone could compromise the security of your Forum.