You can allow your members to sign in to your community using their LinkedIn account.
To start the process, go to AdminCP -> System -> Login & Registration, click Create New to setup a new login method and choose LinkedIn. You will now be prompted to fill in some details which you'll need to acquire by creating an "application" with LinkedIn.
Creating an application with LinkedIn
1. Go to the LinkedIn Developers page and sign in with your LinkedIn account.
2. Click Create App and fill in the form.
3. You will now see your application details. Click on the Auth tab, and then under the OAuth 2.0 settings section, you will see a field labelled Redirect URLs. Click the pencil icon to edit this setting, and add the value shown in your AdminCP. You must click Update at the bottom to save this.
4. Back in your AdminCP, fill in the form, using the Client ID and Client Secret that are shown on the LinkedIn application details screen.