Please do not spam by creating topic after topic. The post here, here and here are all related to your problem of having editing capacity of the files.
Please read carefully how to have command line access to your server. Regardless if you manage to use it now to set the right permissions or not, you will need it in the future. The connection set-up depends on the OS on your computer (it can be Windows, MacOS, Linux...). Read this carefully. When you have ssh access, you should be able to type in commands. There is no graphical interface there - keep that in mind.
As soon as you have ssh access, type in these commands:
sudo chown -R bitnami:daemon /opt/bitnami/apps/wordpress/htdocs
sudo chmod -R g+w /opt/bitnami/apps/wordpress/htdocs
If you cannot set ssh access from your OS (using PuTTY or Terminal), you can use the tool provided by Bitnami in the dashboard:
Just press the "Launch SSH Console" button. There you can type in the commands from above.