You have created an account and want to update your information with your LinkedIn information. This is how you do it.
Go to "my account>my contact information" through the left-side bar. Then click on "link external accounts>add an account".
A screen pops up, enabling you to choose to what kind of account you want to link. Click on the desired choice.
Log in with your account and allow access.
Click on "back to profile" and on "import your profile"
A screen pops up asking you to log in with your account. Now you can choose what information you want to be synchronised. 'Add a message on my LinkedIn Wall' means that your account will share an update on LinkedIn communicating that you have updated your profile on the Holland Alumni network.
Click on "Import selected information" and your information will be updated.
Note that your information will not be synchronized everytime you change something on your LinkedIn account. You have import your profile from LinkedIn again.