What you need to two will depend on if you simply want an export of data into your external software or if you need to obtain live data into it.
The first one is much simpler and would typically involve the following steps:
Dump/log data readings from the RPLidar unit into a file. These readings would be taken in the environment to be measured.
Convert the data to a format that is compatible with your software (there are many format for point clouds and 3D objects).
Import the converted data into your software.
A good starting point for #1 & #2 is the RPLidar SDK from the manufacturer. You can find it on the product page under Useful Links.
Part of #2 and #3 will depend heavily on what software you are using. You will need to look at its documentation for more details.