This is what you need to do
It is relatively easy to switch from Consular Processing to I-485. If your I-140 or I-130 indicates that it was approved for Consular Processing you can go ahead and instead file for I-485 without any extra request or extra steps. You simply file your I-485 application.
However, if the approval notice for the I-130 or I-140 indicates that it is approved for Adjustment of Status and that the INS will hold the case for Adjustment of Status and instead you want to do Consular Processing, the procedure is a bit more complicated. It is then necessary to file form I-824, the request for Consulate notification. According to a September 20, 2000 U.S. Department of State (DOS) cable, upon receiving the receipt notice for the I-824 it is possible to send it with your original approval notice and certain other documentation (mainly the packet 3 forms) directly to the Consulate and request that they schedule an interview. This is a modified version of what used to be called attorney-certified processing, except that the package does not need to be attorney certified.
Though all Consulates are supposed to use the above expedited procedure, many Consulates are not doing that and may instead wait for the case to go through the slower channel: waiting for the I-824 approval and for the cable notification to be sent to the Consulate so that the packet 3 can be generated. From that point, the case would proceed as described in the above question on the CP process in general. Whichever means is used, the case number is then assigned and the interview is scheduled. The Consulate then notifies the applicant by sending packet 4. Packet 4 includes additional instructions, including information about the medical examination, and documents that must be completed before the interview.
