When browsing the forum you can add posts to your Watched list. To do so, you enter the forum, click on the post or forum you want to keep up with and click on the Watch button in the top right corner.
A pop-up will appear asking if you want to watch this forum and receive email notifications or not. Select your preference and click on the Watch button.
The thread/forum will be added to your Watched list, which you can always find at the top of the page.
On a side note, you can also Watch threads as well as Bookmark threads, depending on your preferences. Either click on the Watch button or click on the little bookmark icon on the first post of a thread in the upper right corner:
You can find your Bookmarks by clicking on Alerts at the top, then click Show all, then click on Bookmarks on the left:
A pop-up will appear asking if you want to watch this forum and receive email notifications or not. Select your preference and click on the Watch button.
The thread/forum will be added to your Watched list, which you can always find at the top of the page.
On a side note, you can also Watch threads as well as Bookmark threads, depending on your preferences. Either click on the Watch button or click on the little bookmark icon on the first post of a thread in the upper right corner:
You can find your Bookmarks by clicking on Alerts at the top, then click Show all, then click on Bookmarks on the left: