how can I get Appian environment to practice, I have already opened an account but I have not got the environment
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Sorry, at this point the only official advice on this is to open your account here (which you've already done), then request your Community Edition site via your Profile, which I will assume you've already done, then wait. They advise that current demand is high enough that it can take some time before your Community Edition instance actually gets created due to the current queue. If more than 2 weeks elapse before you get any further automated notification, you could try sending an email to communityEdition@appian.com to ask them to make sure you're still in the queue as normal.
Also please be aware that there is no need to open duplicate posts for the same question here - they all appear on the same front page.