Recently,i created a component and downloaded that component.Now,i want to customize that component according to my requirements.I want to know small thing i.e.

How the text field value will be stored into database? Please provide step by step description.

I searched all the files but i didn't find any "insert sql statement".Please specify the file path which has sql statements that are used to insert the data into database.

This is standard Joomla MVC question.

The model of the concerned table (item model) call the save($data) method to do the job.

If you want to access or change values before or after, just write them in the controller save() and apply() functions.