elm-cookies | Cookies API for the Elm programming language

Because elm-cookies uses a 'native' module, it cannot be included in the Elm package repository. Thus, you cannot install it using elm-package.
Download this respository in one way or another. For instance, you might use: git clone https://github.com/rgrempel/elm-cookies.git Or, you might use git submodules, if you're adept at that. (I wouldn't suggest trying it if you've never heard of them before).
Modify your elm-package.json to refer to the src folder. You can choose where you want to put the downloaded code, but wherever that is, simply modify your elm-package.json file so that it can find the src folder. So, the "source-directories" entry in your elm-package.json file might end up looking like this: "source-directories": [ "src", "elm-cookies/src" ], But, of course, that depends on where you've actually put it.
Modify your elm-package.json to add elm-http as a dependency, if it's not already there. E.g. "dependencies": { "elm-lang/core": "2.0.0 <= v < 3.0.0", "evancz/elm-http": "1.0.0 <= v < 2.0.0", ... your other dependencies },
Modify your elm-package.json to indicate that you're using 'native' modules. To do this, add the following entry to elm-package.json: "native-modules": true,
You would, essentially, be trusting me (or looking to verify for yourself) that the code in Cookies.js is appropriate code for a 'native' module -- that is, that it will not cause run-time crashes or otherwise interfere with the usual guarantees provided by Elm.
It is predictable that this module will need some changes when a new version of Elm is released. Therefore, you would need to remember to check here for such changes when that happens.
It has been said that Elm 0.17 will include additional support for bindings to Javascript platform APIs. This may make this module redundant, or it may make it easier or harder to implement or install.
If you're using this as part of a module you'd like to publish yourself, then you will also be unable to publish your module in the package repository.