<p>It looks like you need to start from basics, ok, no fear. I will try to suggest a simple route to start efficiently to use YOLO techniques. Luckly the web has a lot of examples.</p>

<ol>
<li>Understand <b> <em>WHAT</em></b> is a YOLO method.
<br> <a href="https://www.youtube.com/watch?v=YQYtgzOf9g4" rel="nofollow noreferrer">Andrew NG's YOLO explanation</a> is a good start, but only if you alread know what are <em>classification</em> and <em>detection</em>.</li>
<li>Understand the YOLO <b>Loss</b> function, the heart of the algorithm.<br>
Check the paper <a href="https://arxiv.org/pdf/1506.02640.pdf" rel="nofollow noreferrer">YOLO</a> itself, don't be scared. At page #2, in <em>Unified Detection</em> section, you will find the <b>information about the bounding box</b> detection used, but be aware that you can use whatever notation you want (even invent a new one), in order to be compatible with the Loss function, real meaning of this algorithm.</li>
<li>Start to implement an example<br>
As I wrote above, there are plenty of examples. You can check <a href="https://pythonprogramming.net/introduction-use-tensorflow-object-detection-api-tutorial/" rel="nofollow noreferrer">this one</a> if you are familiar with python and tensorflow.
Inside it you will find <b>a</b> way to prepare the dataset, that is your target for this question, I think. In this case a tool named labelImg is used.</li>
</ol>

<p>I hope it will be useful. Please share your code when it will be ready, I'm curious :). Good luck!</p>
Image segmentation for yolo
<p>For a project I am using <a href="https://pjreddie.com/darknet/yolo/" rel="nofollow noreferrer">YOLO</a> to detect phallusia (microbial organisms) that swim into focus in a video.  The issue is that I have to train YOLO on my own data. The data needs to be segmented so I can isolate the phallusia.  I am not sure how to properly segment/cut-out the phallusia to fit the format that YOLO needs.  For example in the picture below I want YOLO to detect when a phallusia is in focus similar to the one I have boxed in red.  Do I just cut-out that segment of the image and save it as its own image and feed to that to YOLO? Do all segmented images need to have the same dimensions?  Not sure what I am doing and could use some guidance.  <a href="https://i.stack.imgur.com/htx16.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/htx16.jpg" alt="In focus phallusia"></a></p>