The basic commands are:
devtool -list
Which gives you a list of possible tools and versions. All depending on what your organisation/company has made available.
devtool -install
The install command is the one that does the job. You can use eg:
devtool -install jdk
This will install the latest version of the jdk. Or you can use the following to install a specific version:
devtool -install jdk 1.9