When ever you activate Flexi Plugin the few pages are created automatically for you easiness.
One of the page is ‘Post Image’ & ‘Edit Flexi Post‘ and it has various fields and this is generated with following shortcode for ‘Post Image’.

[flexi-form class="pure-form pure-form-stacked" title="Submit to Flexi" name="my_form" ajax="true"]
[flexi-form-tag type="post_title" title="Title" value="" placeholder="main title" required="true"]
[flexi-form-tag type="category" title="Select category"]
[flexi-form-tag type="tag" title="Insert tag"]
[flexi-form-tag type="article" title="Description"  placeholder="Content"]
[flexi-form-tag type="file" title="Select file" required="true"]
[flexi-form-tag type="submit" name="submit" value="Submit Now"]
[/flexi-form]

• Title
• Category
• Tag
• Description
• Select File
• Submit button

This page is generated with [flexi-form] shortcode and each fields is inserted with [flexi-form-tag] shortcode.
All you have to do is remove that shortcode from the page.
For example you want to remove ‘Tag & Description’ from the page.

Tag has shortcode of [flexi-form-tag type="tag" title="Insert tag"] & Description has shortcode [flexi-form-tag type="article" title="Description" placeholder="Content"]

So, edit the page where which has the form and remove that shortocode. Which results the shortcode as below.

[flexi-form class="pure-form pure-form-stacked" title="Submit to Flexi" name="my_form" ajax="true"]
[flexi-form-tag type="post_title" title="Title" value="" placeholder="main title" required="true"]
[flexi-form-tag type="category" title="Select category"]
[flexi-form-tag type="file" title="Select file" required="true"]
[flexi-form-tag type="submit" name="submit" value="Submit Now"]
[/flexi-form]

Save or Publish the changes. Now it will have fields as

• Title
• Category
• File
• Submit

Similarly, if you have activated Flexi-PRO can let users to modify the submitted post. Which is dynamically created as ‘Edit Flexi Post‘ page. This page can also be modified as above steps.