Before going any further, follow the advice printed on the front cover of your copy of The Hitchhiker's Guide to the Galaxy:
Don't Panic.
Next, read "
SECTION GUIDELINES - PLEASE READ BEFORE POSTING HERE" (it's in all caps for a reason).
This section is for questions related to problems installing/running the game on your PC. By 'PC', we mean the versions running under Windows (XP/Vista/7/8/10), MacOS (10.9.5, 10.10), and Linux (Ubuntu 14.04 LTS) on a desktop/laptop computer. Examples of the types of questions appropriate for...
forums.terraria.org
And here's a very detailed post on troubleshooting.
Troubleshooting Terraria Issues Supports 1.3.5.3 - 1.4.0.3 Table of Contents About System Requirements Dependency Requirements Identify The Problem Up-To-Date Graphic Drivers Terraria Launch Failures Using TerrariaServer.exe The Common Errors No Suitable Graphics Card Found .NET Framework...
forums.terraria.org
If you provide sufficient information, it might (or might not) be possible for others to determine what's wrong and help you to fix it. If you don't provide necessary info, it's almost certain that nobody will be able to randomly guess the solution to a problem that you've not described meaningfully.
Think about it. You phone an auto mechanic and say, "My car doesn't work! It has tires and a radio antenna but it won't run!" Three frustrating (and in the real world, expensive since mechanics gotta be paid) hours later the mechanic says, "When I asked earlier, you said it's an old car with a gasoline engine. How much fuel is in the tank?"
"… um. Fuel???"
Provide the info the mechanic needs right up front. Save her*, and you, a lot of time and effort. Good luck!
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* nope, different mechanic; this one doesn't use a pipe wrench