BuddyPress.org

1) Read this.

2) It sounds like you’re using regular WordPress. Your users will need to be setup with the default role of “Contributor” or higher. You can set this on the “Settings > General” page in the WordPress admin area:
https://codex.wordpress.org/Settings_General_SubPanel

Then you can try installing a front-end posting plugin. Read this thread for more details:
https://wordpress.org/support/topic/304606