lavaan is implemented as an R package. This means that before installing lavaan, you should have installed a recent version (>= 3.0.0) of R. You can download the latest version of R from the R-project website.
Once you have installed R, you can install the lavaan package simply by starting up R, and typing
To check if the installation was succesful, you can load the lavaan package and try one of the examples. For example:
If you can see the output, everything is set up and ready.
Now that you have installed lavaan, you can: