Please go through the below link for creating a shopware theme.
In this blog, We are going to create free text fields for a custom theme that extends the tpl files to be shown on the details page in shopware 5. To create these text fields follow the below steps.
The custom directory is a theme that I created already.

Step 1: Log in to the admin panel and go to the Configuration > Free text field management.

Step 2: Click on the Add item to create new text filed.

Note: Make sure you selected item (s_articles_attributes) table .

Step 3: Fill the required filed. And save it.

Note:
Database configuration:-
Column name: Name the column which is store in the shopware database.
Column type: You can select types of text.
View configuration:-
Label: Name the label shown on the detail pages.
Display in backend: Enable this to display in the backend.
Step 4: Now go to the Items > Overview.

Step 5: Edit the item by clicking on the pencil icon.

Step 6: After clicking on the edit, scroll to the last page. And add value in the Dimension field. Save the items.

Step 7: Go to the shopware theme directory of your website.
Step 8: Create a new file in the theme directory called “buy_container.tpl“
File Structure:–
themes>Frontend>Custom>frontend>detail>content>buy_container.tpl.

Step 9: In “buy_container.tpl” write this code.
{extends file="parent:frontend/detail/content/buy_container.tpl"}
{block name='frontend_detail_index_buy_container_base_info'}
{$smarty.block.parent}
{* Product attribute 4 *}
{if $sArticle.attr4}
{s name="DetailAttributeField3Label" namespace="frontend/detail/index"}Dimension{/s}:
{$sArticle.attr4}
{/if}
{/block}
Save the files and Clear the cache.
Step 10: Open the product which you added in the dimension field.
