First thing you'll need to do is create a webserice role and assign a webservice user to it.

Go to System > Web Services > Roles

Click the "Add New Role" button on the top right of your screen.

Make up a role name like "webuser" or something.

Give your new role premission to all your resources so it can get your attributes from your webshop and import your products.

Then just save this role!

Then go ahead and create a webservice user

Go to System > Web Services > Users

Click the "Add New User" button on the top right of your screen.

Make up a some account information and be sure to remember the API Key.

Now assign this user to the role you created before.

Now go back to the top of this website enter your website and e-mail and go go go!