If you want to add a ad unit in Top left corner of your post then just include following lines in your ad code.
<div 0px;”="" 0px="" 10px="" style="display: block; float: right;">
Your Adsense ad script
</div>
Just change the <div> float tag to “right”, if you want to place ad unit at right corner. The 250×250 square ad unit is most appropriate for this ad placement.
If you are using adsense delux or Adsense Manager plugin for ad management then add the same code before and after your ad tag. i.e
<div 0px;”="" 0px="" 10px="" style="display: block; float: right;">
<–adsense unit name–>
</div>
Adsnese unit in middle of the post disturb the reading flow so its better to have ad units at the begging of the post. If you have any query adding this ad unit in your blog post let me know.