WP doesn’t have a built-in way to restrict permissions this granularly. You can either install plugins, or not.
For settings, it depends on where the plugin surfaces its settings. For example, if the settings are under the “Settings” menu, then by default only users with role “administrator” will be able to access and adjust them. (Similarly, any user with role “administrator” will then be able to access and adjust any settings under that menu.) If the plugin’s settings are under the “Tools” menu, then by default users with role “editor” will be able to access and adjust them (and any others under that menu).
Installing a plugin should be as straightforward as:
Step 1, load the code: if the plugin is in the WP repository, any admin can search and install it. If it is not in the repository, an admin can upload the plugin’s .zip file through the plugin installer.
Step 2, activate: the admin hits “activate” in the plugins listing.
So, you may wish to install the plugin yourself, and then only provide whatever specific access the freelancer will need to adjust settings (keeping in mind that this may also involve FTP access to files if it’s a more complex plugin).