Adding Previous and Next Links on Oxygen Single Post Template is Really Simple

Add two code blocks

One for Previous Post Link and Other for Next Post Link

For Previous Post Link Code

<?php
if ( get_previous_post_link() ) {
    previous_post_link();
}
?>

For Next Post Link Code

<?php
if ( get_next_post_link() ) {
    next_post_link();
}
?>

This is the simple and easiest way to add Next and Previous Post Link on Oxygen Single Blog Post Template

You can customize the design with css to make it look more professional and related to your theme.