LinkedIn can be used for finding a job, by doing an active job search or by letting other people now that you are open to new career opportunities. This is how you can do it with few simple steps.
Log in your LinkedIn account and guide you mouse pointer at you picture, which is located at upper right corner. Once your mouse pointer is there a small window will appear.
At the drop down window select Privacy & Settings
Then you'll be guided in the Privacy & Settings page of your account.
Click on the Communications tab and then click on the 'Select the types of messages you're willing to receive'.
A small window will open and then you can select in which cases other people can contact you but also which state is visible to other people. Select 'Career opportunities' and more if you want. Adjust the message in the text box and then save your changes.