I want to enter the Theme settings in the settings as in the bender theme for example in the panel administration banner advertising areas.
In admin settinging I added attach code to post
and css code:
.ads_300,.ads_728,.ads_468{background-color:#FDF6E5;display:block;margin:15px 0}
.ads_300{width:300px;min-height:250px}
.ads_728{width:728px;min-height:90px}
.ads_468{width:468px;min-height:60px}
.ads_header{width:728px;margin-left:auto;margin-right:auto;padding:10px 0px 10px 0px}
.ads_header,.ads_300,.ads_728,.ads_468{display:none}

In the header page I've entered:
    <!-- header ad 728x60-->
    <div class="ads_header">
    <?php echo osc_get_preference('header-728x90', 'elena'); ?>
    <!-- /header ad 728x60-->

I do not know how and where to set the areas where ads will appear or what exactly I have to do.
Can you help me please.

You can put adsense code to item.php
Personally I do not recommend to put more than 1 banner as it impact user experience in very negative way.

thank you for the advice
Ok but how do I manage to put in the admin panel
It's easier not to go into the cPanel when I change my ad every time.
I fail to make the code work and I do not know how to define the area where the code will appear.
Can you help me please.

Elena theme does not have such functionality, you can look on Banner Ads or Advertisement Manager plugins.

Thank you
I will still try to create a space from the admin panel so that a banner300 * 250 to appears on the ad detail page.
If you can help me thank you

Sure you can, but such feature is not on plan from our side.

Thank you but they are not what I needed.
I managed to make the code so now in the admin panel I can set the ad to appear on any page of the web site.
Solved.