Before you ask for a solution you need to understand why you WP is asking for FTP credentials. This is because WordPress enviroment does not have permissions to access plugins folder. You need to change permissions for these folders. Kindly never change wp-content or any folder under this folder to permission 777. I recommend setting any or all folders under wp-content to 744 - gives permission to owner (username that uploaded or installed) and gives all others read only access.
A common workaround for this is adding the define('FS_METHOD','direct');
directive in wp-config.php