This is a simple steps on how to download rebirthro installer.
First, go to rebirthro website: http://rebirthro.com/
Click on Download button at the left top of the website & u will be directly to next page.
Now, you have 2 options to download the installer. Go for direct download or using Bittorrent. If you choose to direct download, click on the link below it. And the download process will start. I dont really recommend direct download because if somehow u got disconnected from internet, ur download will be corrupted & u need to download from the start again!
Download via Bittorrent is the best choice. What u have to do is to click download link below it to get rebirthro torrent files.
Click on the rebirhro torrent files & a new window will pop up as u can see in the screenshot below, what u have to do is click ok to start download.
After u click ok, the download will be started. Now, u just need to wait until it's done. While waiting for it, start making a new account so u can play it when the game already installed inside ur pc/laptop.