As @bulgaru mentioned, you can edit the php.ini file and restart all the services or modify the specific configuration of WordPress. In the second case, you'd need to edit the httpd-app.conf file that you'll find at /opt/bitnami/apps/wordpress/conf and insert this piece of code inside the Directory block.
php_value max_execution_time XXXX
One of our main goals is to configure Bitnami applications in the most secure way. For this reason, we moved the configuration in the .htaccess files to the main application configuration files and set the AllowOverride option to None by default.
The content of the .htaccess files have been moved to the /opt/bitnami/apps/APPNAME/conf/htaccess.conf file.
In case you've installed any plugin that creates a .htaccess file, you'll need to copy that information to the htaccess.conf file.