From the Mac App Store:

The Mac App Store makes purchasing, installing and registering Apps very quick and easy.

Simply select the 'Buy' option for RapidWeaver and enter your Apple ID (if needed). The App Store takes care of the rest and places RapidWeaver straight into your Dock with no need to register it! If you're prompted to enter a serial number, despite buying RapidWeaver on the Mac App Store, you should ensure that you remove RapidWeaver from your Mac and reinstall it from the Mac App Store.

For more information on RapidWeaver and the Mac App Store take a look at the following FAQ on our Knowledge Base.

From the Realmac Software website:

Downloading, installing and registering RapidWeaver directly from Realmac Software is also very simple.

1. Download the rapidweaver.zip file from the RapidWeaver page on our site.
   
2. Once the download has completed, open the ZIP file found in your Downloads folder.
   
3. Drag RapidWeaver from the Downloads window to your Applications folder in the Finder.
   
4. Locate RapidWeaver in your Applications folder and launch it!

Note: If you have downloaded RapidWeaver from our site, you are welcome to run it in demo mode for as long as you like. However, the demo limits your project to only three pages.

When RapidWeaver launches for the first time, you will be prompted to do one of three things:

• Purchase RapidWeaver (either within RapidWeaver itself or online)
• Enter a valid serial number
• Run RapidWeaver in Demo mode

After you’ve made your choice, go ahead and create a new project by using the ‘Create a New RapidWeaver Project’ button and you're ready to get started.

Figure 1: The Projects Window (new to RapidWeaver 5)

What's Next?

Now that you've learnt how to Install & Register RapidWeaver take a look at Adding Pages To Your Project.