I added this code to the template , do i need to do something else?
$limit = 2; // comments to display per page
$start = ($input->pageNum-1) * $limit;
$selector = "page=$page, sort=-created, start=$start, limit=" . ($limit+1);
// find the comments. replace "comments" with the name of your comments field
$comments = FieldtypeComments::findComments("comments", $selector);
// output the comments
echo $comments->render();
// output the pagination links
if($input->pageNum > 1) echo "<a href='./page" . ($input->pageNum-1) . "'>Back</a> ";
if(count($comments) > $limit) echo "<a href='./page" . ($input->pageNum+1) . "'>Next</a>";