First, you need to be registered online with the national LTC Guild. Then --
1. When logged in, click on the Chapters tab.
2. Click on the name of the chapter you want to join; this takes you to the chapter's page.
3. Under Admin Options to the right of the Information column, Click on Join ... (followed by the name of the local).
That's all there is to it! You're now included in the Local's membership roster, and will receive notices of chapter activities. To confirm that you're registered with the local, refresh the page and look under the Members heading (right below Admin Options). You should see your picture, which is hot-linked to your personal page.
NOTE: If you already belong to the local but don't know it, and try to join, you will NOT see the link to join. It is only visible to logged-in members who have not yet joined the local.
Also, if you try to join when not logged in to the national site, you will NOT see the Admin Options, and will not be able to join until you log in.