First you should add new field via your administration:
Admin->Real estate->Fields (You can see # part there, what is field ID)

Then you should add it to your template file property.php

{estate_data_option_#}

Where # represents field id / key of option

You can also use alternative PHP syntax, for example:

<?php if(!empty($estate_data_option_#))echo $estate_data_option_#; ?>

More details are available in documentation:

http://iwinter.com.hr/real-estate/documentation/#!/property_template

To add new category, most simple way is to just copy example code from another category and modify by your needs.

Or use this code example:

<?php

    $category_id = 1;

?>

<?php if(isset(${"category_options_$category_id"}) && ${"category_options_count_$category_id"}>0): ?>
<h3 class="page-header"><?php echo ${"options_name_$category_id"} ?></h3>
<div class="property-amenities clearfix">
    <ul>
        <?php foreach(${"category_options_$category_id"} as $key=>$row): ?>
        <?php if(!empty($row['option_value'])): ?>
            <?php if(count($row['is_text']) > 0): ?>
        
            <div class="panel-row"> 
                <p class="bottom-border"><strong><?php _che($row['option_name']); ?>:</strong> <span><?php echo _che($row['option_prefix']); ?> <?php echo _che($row['option_value']); ?> <?php echo _che($row['option_suffix']); ?></span><br style="clear: both;" /></p>
            </div>
            
            <?php elseif(count($row['is_dropdown']) > 0): ?>
            
            <div class="panel-row"> 
                <p class="bottom-border"><strong><?php _che($row['option_name']); ?>:</strong> <span class="label label-success"><?php echo _che($row['option_prefix']); ?> <?php echo _che($row['option_value']); ?> <?php echo _che($row['option_suffix']); ?></span><br style="clear: both;" /></p>
            </div>
            
            <?php endif; ?>
        <?php endif; ?>
        <?php endforeach; ?>
    </ul>
</div><!-- /.property-amenities -->
<?php endif; ?>