You asked how to get out of LinkedIn. You can try changing your account so you don't get any messages or you can close your account.
To change your message options:
Sign in to LinkedIn - here
If you cannot remember your password, click on the "Forgot password?" link. You will be sent an email to reset your password which will allow you to sign in.
After you have signed in, there is a drop down menu on your name at the top of the page. Mine says "Sue Welsh v". Mouse over that and click on the "Settings" to go to the Setting page.
At the bottom left of this page, are a set of menu tabs: Profile, Communications, Group (and stuff) and Account. Click the Communications item. It will expose the following menu:
Emails and Notifications
- Set the frequency of emails
- Set push notification settings
- Select the types of messages you're willing to receive
- Select who can send you invitations
There are a bewildering set of apparently similar items. You can set them all to "No email".
You can also close your account if you want to do this.
p.s. Most social networks or websites with logins have an equivalent function. They don't really want to annoy you! They have help pages that are useful, but they are often confusing if you don't understand the language or what is happening behind the scenes.