If you have not done so already, arrange with Mathworks Sales to have the toolboxes added to your license.
(There are ways in which it is possible to install a toolbox without having a license for it already; it just is not as common as already having a license.)
After that, when you install the toolboxes, normally MATLAB would automatically update the license. However, if it does not, then at the right hand side of the toolstrip on the main command window,
Resources -> Help -> Licensing -> Update Current Licenses...
The major exception to this would be if you are using a network license, in which case the license administrator would add any necessary licenses to the license directory, and then would tell MLM to have another look at the licenses. (On Unix systems, traditionally that was by sending a signal 1 to the MLM daemon... but that was a long time ago...)
