how to link my pdf file in html code example

Example: html link to pdf

Since you have not clarified for us whether you are using a local host or just viewing the text file in the browser I will assume the latter.

In this case, you would have your anchor tag and in the href attribute put the location of the file

<a href="C:\Users\Shannon Myers\Documents\Biology-DNA\teen_time_report.pdf">ok</a>
In the above example I started from my C: drive and went from there. Also you could do it as follows:

<a href="Resources\teen_time_report.pdf">ok</a>
This should link to the pdf file that you have in mind, as long as the resources folder and html file are in the same folder