I have built a gpEasy site at my domain.com/gpEasy, and I want to get it live at my domain.com.

I've tried reinstalling gpEasy at my domain.com, but instead of the installation page I get a blank one. 

What do I need to do to get my site active?

I'd recommend the folloging steps:

1. Get a text editor that supports search and replace for multiple files.
    Under Windows I use Notepad++ for that purpose. It's free + open source (GPL).   

2. Copy your entire /data directory and the .htaccess file from your gpEasy Installation
    to a folder on your local computer.
     Make a backup copy of this file/folder in case something goes wrong!

3. Open the .htaccess file
    Perform a search and replace* in your .htaccess file and in all files in your /data subdirectory:
    Replace /gpEasy/  with /

4. Copy/Overwrite .htaccess and /data/* in the gpEasy installation on your server.

Now everything should work.
(Keep your backup copies until you have checked your entire site!)

* In Notepad++ it's located in "Search" Menu -> "Find in Files". Check the checkboxes "Directory of the active file" and "Subdirectories"

Another note: I have tested a bunch of search and replace tools and quite a lot of them mess up the encoding of the files - which must remain UTF-8.
Notepad++ get's this right. If you use a different editor keep an eye on possible umlauts, diacritics and other non ASCII characters!

HTH