Putting together the OPT application package is easy compared to the wait you must endure while USCIS is processing it.It can, at this time, take anywhere from two to five months to get an answer from them, probably closer to 3-4 months.If you sent your OPT application in the last few weeks, it may be that they haven't even opened the envelope yet; they will normally send you a notice saying that they've received it and are processing it once they do begin looking at your application. At that point, the notice online should acknowledge that it is being processed. So, if it's only been weeks, I would wait a bit longer. If it has been over a month since you sent it, I would call the number provided and ask about it.If you included the Form G-1145, their response to it should be the first indication that they received it and it's in process. If you included it and haven't heard back from USCIS by email, then I would worry that it's been lost in the mail.Call the number, talk to a human, and find out if it's been received and when the case status indicator will be updated online. After that, just sit back and wait and don't worry.