Album Scrobbler is a desktop application that allows for the quick scrobbling of albums, or collections of selected songs on last.fm. This is especially useful for people who listen to music in a way that doesn't get automatically scrobbled, or who have issues with an auto-scrobbler breaking from time to time.
In order for this app to be able to send scrobbles to your account, you need a last.fm API Account? Why? I'll explain after the setup instructions.
First, you need to register for an API account. This is very simple and can be done here. All you need to fill out on this form is an email, and the name of the application (probably "Album Scrobbler" for simplicity).
(screenshot of registration)
Now, this should bring you to a page that looks like the following screenshot. You can copy your API Key and Secret from here, and paste them into the boxes within the application.
(screenshot of api key)
(screenshot of form in app)
Once you have saved your keys, you may proceed to login with last.fm in the application and scrobble away!
The last.fm API is something that essentially gives this application permission to do things to your account (e.g. send a scrobble). The reason that I can't just use my API account for everybody comes down to the API Secret. There would be no feasible way for me to provide it in the code/some other method without someone being able to gain access to it, and then possibly mess with my API account/do other bad things. Having to create your own account is the compromise that has to be made for this to work from a desktop application that doesn't have anything running on a server somewhere else. The way that last.fm handles this for websites is different, which is why they are able to have a simple "sign-in with last.fm" button. Sorry for the inconvenience but this is just how it is (at least for now).