You have to get a new one at the same place you got the last one. If that was through a school, then they have the necessary steps to enable you to get one as lomng as you are a student. Otherwise, you get one trial per user name
thanks. but i downloaded the arcgis desktop from the esri website. am
not looking for another free trial but the 'full' or 'pro' version. am
willing to pay but don't know where or how to do that.
This might give you a starting point to find your local distributor.
Nigeria is on the list. With a "current" Desktop, you typically get one AGOL and Pro license with that. A new purchase typically comes with the first year maintenance (that is, current). If you don't continue on maintenance after the first year, Desktop continues to work, but at least at this time, AGOL and Pro would not (those are annual subscriptions) I know that is maybe more info than you needed at this time, and your local distributor could fill you in with the details. I mention "typical" on all of that because I am in the U.S. and it is possible that it is different thru a distributor outside of the U.S., I'm not sure.
I hope that helps.