IDK why you would get that, but basically it means what it says: the code has indentation at the start of the file. Ren'Py uses indentation (spaces,
never tab characters) in its code to indicate subsections. (Python, upon which Ren'Py is based, does this as well.) For example, when a menu appears, you'll have something like the below.
Python:
menu:
"menu choice 1":
---STUFF HAPPENS HERE---
"menu choice 2":
---OTHER STUFF HAPPENS HERE---
Because indentation indicates that things "belong" to what's above them ("---STUFF HAPPENS HERE---" is a part of picking "menu choice 1", and so on), the beginning of the script file should never have indentation. It's the beginning of everything and so isn't dependent on anything else in the game.
I do not know how you got the first line indented, though, but I think you should be able to fix this. Close the game completely and then open the
\game folder (wherever you have the main folder for
How It All Began saved). With that open,
right-click on the file called
script.rpy and open it with even a basic text editor. Delete any indenting from the very first line of the file and then save it again. Finally, you want to delete the RPYC that's normally automatically generated with the game; so locate
script.rpyc if you can and delete the file
if it exists (it's possible it's not there). Now restart the game and the error should hopefully be gone.