Problem:

How to create a form to set the site logo in the front end form.

Solution:

In most cases, the WordPress site logo value is stored in your database "wp_options" table, but Toolset Forms can not manage data in that table, so there isn't such kind of built-in feature within Toolset Forms.

And in your case, you can consider custom codes, for example:

Relevant Documentation:

https://toolset.com/documentation/programmer-reference/cred-api/