[ToXiiC]

Navigate to,
Admin CP > Templates & Styles > Templates > Select your default theme > Header Templates > header_welcomeblock_member

Once you are there, find were it says,

Code:

<a href="{$mybb->settings['bburl']}/search.php?action=getnew">{$lang->welcome_newposts}</a> | <a href="{$mybb->settings['bburl']}/search.php?action=getdaily">{$lang->welcome_todaysposts}</a>

Add this:

Code:

| <a href="search.php?action=finduserthreads&uid={$mybb->user['uid']}">View my threads</a> | <a href="search.php?action=finduser&uid={$mybb->user['uid']}">View my posts</a>

Post any questions or comments below.
Written by,
ToXiiC