Some apps require editing the config or .env file to configure app options.
Over YunoHost the app configutation files are usually located at:/var/www/app_name/
or/home/yunohost.app/app_name/
You can SFTP to that directory and edit the configuration file. Check out the app documention for the config file name and parameters.
After editing the config file, you may need to restart the app. For that, go to Tools > Services > App Name and then click on “Restart“.