from 1.2 to 1.3 there is no DB changes
backup your app/Config/bootstrap_app.php file and compare with new version so you can merge your settings.
download phkapa-1.3.zip and replace old version
you can also use git pull or composer update features
if you have made changes to phkapa code, then it's a good idea to use git pull to update or use diffmerge tool or similar