How to Join LinkedIn without an Invitation
When you click the button, you're taken back to LinkedIn and it confirms your address. You may be asked to log in to your account, so simply provide your e-mail address and password when prompted.
You are asked to connect your e-mail account to look for new contacts, prompted to install the LinkedIn mobile application, and offered the chance to upgrade your account to a paid account. You can always click Skip This Step to move along the account creation process and save those tasks for later.
If you skip this step of confirming your e-mail with LinkedIn, you won't be able to invite any connections, apply for jobs on the LinkedIn job board, or take advantage of most other LinkedIn functions.