on joomla frontend submission you can upload intro and full image images using joomla media manager. You first upload on the folder you choose and then select image and then insert image. I need to change that behavior, i want to upload image directly to specific folder without using media manager. Just select your image and then upload. How can i make this happen? Can i make it using template overrides?
I highly suggest using the Joomla Content Editor (JCE): https://www.joomlacontenteditor.net/
It's free and you can install and make it the default editor for your site. Once installed, its image manager overrides the core one, so when you click on Intro/full image, it pops up that dialog where you can upload directly there.
You can also drag and drop into the body of the article if you do not want to see any popups. However, if you wanted to assign as the Intro/Full Image on the "Images and Links" tab, you would have to know the file name and manually input it. So if your default folder was /images/ and you did a drag/drop of sample.jpg, you would have to type into the Inntro Image field: images/sample.jpg
Here is a demo if you want to check it does what you need it to: http://demo.joomlacontenteditor.net/