This question has been answered on this forum probably 100+ times.
To teach you to help yourself: Paste the error message into the search box on this forum, or even in a generic search engine. That would have gotten you a quicker result then creating your post and the 7 minutes you waited before I posted this reply.
Use the net highlighter tool which will show you that +3.3V and GND are the same net due to this short. Then use the find tool to look at instances of +3.3V one at a time. This kind of error is hard to track down so be more careful when drawing schematics.