In order to place donate button in center of block you should follow these steps. 

1. Select `Edit` in block where donate button is placed

   Then you will be moved to edit mode

2. Select 'Edit' for block.

   Then iframe embed code for donate button should be displayed. 

   <script src="...">

   <a class="dbox-donation-button" href="..."...></a>

3. Add new div tag with `donate-button` class above this code. 

    <div class="donate-button">

       <script src="...">

       <a class="dbox-donation-button" href="..."...></a>

    </div>

4. Add stylesheet for centering below div tag.

    <div class="donate-button">

       <script src="...">

       <a class="dbox-donation-button" href="..."...></a>

    </div>

   <style type="text/css">

        .donate-button {

           text-align: center;

        }

   </style>


Then you are done!

Check your website. :)