1. inform your current CA atleast 3 months in advance regarding your intention to go for industrial training.
2. once you finalise the company you want to intern with, on the due date, execute form 109 with the current principal along with a covering letter from your principal stating that this form 109 has been executed as you wish to go for industrial training.
3. execute form 104 with the company and send form 104 and 109 to ICAI along with the cover letter.
4. please note that you should have cleared both groups of IPCC and should have atleast 9 months of articleship pending.