If these are static instructions (they generally won't be changing), you could craft an EE Accessory to just insert a new element on the CP Home Page with your instruction in them.
https://ellislab.com/expressionengine/user-guide/development/accessories.html
Here's a pseudo-ish-code example:
function set_sections()
{
// Check to see if you're on the CP Home Page
// if not, return false
// use the ee()->cp->add_to_foot() to add jQuery to insert stuff
// kinda like this:
ee()->cp->add_to_foot('
$(document).ready(function(){
$("#mainContent").prepend("<div class=\"contentMenu helptext\" style=\"width: 93.6%;margin-bottom: 1em;\"><div class=\"heading\"><h2>Help Text</h2><ul class=\"homeBlocks item\"><li>Help! I need to tell you all the helping things!</li></ul></div></div>");
});
');
}
And tada!

Edit Welp, if it's something you need to change constantly, here is one option. Store a snippet with your instructions, and dump that instead of static stuff. Call your snippet cp_help_text
or something. Snippet content:
<div class="contentMenu helptext" style="width: 93.6%;margin-bottom: 1em;">
<div class="heading">
<h2>
Help Text
</h2>
<ul class="homeBlocks item">
<li>
Help! I need to tell you all the helping things! Easily changed from the Design -> Template -> Snippets.
</li>
</ul>
</div>
</div>
And back to the accessory:
...
$snippet = ee()->db->select()
->from('snippets')
->where('snippet_name', 'cp_help_text')
->get()->row_array();
ee()->cp->add_to_foot('
$(document).ready(function(){
$("#mainContent").prepend("'.$snippet['snippet_contents'].'");
});
');
....
Yup, seems convoluted! Perhaps someone can give you a better answer.