The fourth step of your X-Cart v4 store migration to v5 is to switch your old XC4 store to the new XC5 one and make your new XC5 store live.
Before making your new XC5 store live, make sure it has been perfectly set up, all the functionality matched, and the data transferred.
For details, see:
To make your new X-Cart 5 based store LIVE:
Close your old X-Cart 4 based store as described in the Common store options guide of the X-Cart 4 Knowledge Base.
Move the closed X-Cart 4 based store into a subdirectory described in the (Moving Store to Web-Root Directory guide of the X-Cart 4 Knowledge Base.
Move your new X-Cart 5 based store to the original location of the old X-Cart 4 one as described in Moving X-Cart to Another Location.
In case you prefer launching a new X-Cart 5 store on a different server (variant 3 from Does X-Cart 5 Have to Be On the Same Server?) and want to make it live there, make sure the server paths of your XC5 based store are the same as the corresponding paths of XC4. This is extremely important to keep SEO ranks at the same level after the switch.
Perform the final data synchronization between your old X-Cart 4 and the new X-Cart 5 stores.
Set up redirects so Google can find your pages at their new locations.
Launch your new X-Cart 5 store.
The final data synchronization and redirects set-up are described in detail in the guides below.