I want to search a word and then want to insert a new line. how i can achieve this
You may try to use Find/Search options provided via Aspose.Cells APIs to search specific string in the cells in the worksheet, see the document with example code for your reference:
Regarding insert a new line, do you need to add line break in the cell (value) or you need to add a new cell/row? Please provide your expected Excel file (you may manually create the file into Ms Excel) for reference, we will check and help you accordingly.
PS. please zip the file prior attaching.