I'm still not sure about the system. Could you tell me how soon I have to choose the best answer? Because a few days after posting a question, there is no way for me to accept an answer. Sometimes I am able to choose an answer.
I'd like to know how soon I need to accept and answer, and for how long I am able to accept one.
The problem was that the first question you posted was with an unregistered account. You have since registered, so you were able to accept questions under your registered account, but the other question didn't recognize you as its owner.
I've had the Community Team merge the accounts, and the question now appears on your question list. You should be able to accept an answer now :) Let me know if you have any other problems!
Wendikidd answered about what happened in this specific case. I will answer about how soon an answer should be accepted.
There isn't a limit to when an answer should be accepted, and nobody should push you to accept an answer in the first two hours the question has been asked.
Blindly accepting the first given answer without giving to other users the time to answer your question is counter-productive: It could be the first user who answered misunderstood the question, or the given answer is incomplete. Since you are asking the question, chances are that you don't know the correct answer; you depend on the others to tell you which is the correct answer, and that is done on Stack Exchange with comments, and votes.
When I see the sole answer being accepted few minutes after being written, I always think that:
I'm always in favor of waiting at least half a day, if not a full day. I think it's a bad practice to accept an answer within just a couple hours of posting; it's better to let the rest of the community have a look and possibly weigh in before accepting an answer.
I'm only stating my opinion on this, but I've often seen an ELL user accept the first answer that came along, sometimes within minutes of the question being asked. I've even seen a few rare cases where an answer with erroneous information was accepted – that's not doing anyone any good. I suppose users can do whatever they want to do, but I think it would be better to wait a bit.
