Simplicity is easy to use gallery plugin that allows you to create and manage image galleries just dropping the files into a folder of your choice.

Noted That:

To install correctly this simplicity-gallery.zip.
Fisrt Download the simplicity-gallery.zip to your computer
Extract/Open simplicity-gallery.zip to Your Computer.
Then, Find readme.txt file inside simplicity-gallery.zip and Open readme.txt.
Now, Read the Requirements of this plugin. Which Wordpress Version and PHP Version are required to run this Plugin in Your Wordpress Site.
Then, Follow the the Tips Below.

Start the Tips:

1. First Download "simplicity-gallery.zip" Plugin to your Local Computer. (Click Download)

2. Then, Login to your "yourdomain.com/wp-admin" Dashboard.

3. Then, Click on "Plugins" + "Add New" from left sidemenu of Dashboard.

4. Now, Click on "Upload Plugin" button.

5. Now, Browse "simplicity-gallery.zip" Downloaded plugin from your computer, Where you downloaded simplicity-gallery.zip According to Step – 1 Above then, click on "Install Now"

6. Now, Click on "Active Plugin"

7. Then, See left sidemenu. "Simplicity – WordPress gallery plugin" folder is added on left sidemenu. Now, Click on "Simplicity – WordPress gallery plugin" folder.

Noted that: If you do not see "Simplicity – WordPress gallery plugin" folder on left sidemenu then, see at left sidemenu "Settings" or "Tools".

8. Now you configure yourself oR Watch video tutorial below about Simplicity – WordPress gallery plugin Configurtions and Settings or How to work "Simplicity – WordPress gallery plugin" in your WordPress site.

After Activated Plugin According to Step-6 then,

Go to "Plugins" + "Installed Plugin" from Wordpress Admin Panel Leftside Menu.
or Direct go to: https://yourdomain/wp-admin/plugins.php
Then, Find "Simplicity – WordPress gallery plugin" Activated Plugin from Plugin List.
Then, Click on "Settings" from Plugin that is Simplicity – WordPress gallery plugin
Now, Edit/Add/Config the setting and Click on "Save Changes" button,

Guide
INSTALLATION: The easiest way to enjoy Simplicity Gallery is to login to you WordPress dashboard, go to Plugins >> Add New, search for Simplicity Gallery, and click to install. You can also download the zip file from this page and upload it from the Plugins >> Add New > Upload page. HOW TO USE: Just go to a page or post and bellow the editor window you will see the Simplicity configurations. If you want to attach a gallery to your post or a page just type the name of the images folder where your files are located. Please note that directory should be accessible from the web server to write. DOCUMENTATION: Just check Simplicity Gallery Documentation for more information regarding options.

Guide

INSTALLATION: The easiest way to enjoy Simplicity Gallery is to login to you WordPress dashboard, go to Plugins >> Add New, search for Simplicity Gallery, and click to install. You can also download the zip file from this page and upload it from the Plugins >> Add New > Upload page.

HOW TO USE: Just go to a page or post and bellow the editor window you will see the Simplicity configurations. If you want to attach a gallery to your post or a page just type the name of the images folder where your files are located. Please note that directory should be accessible from the web server to write.

DOCUMENTATION: Just check Simplicity Gallery Documentation for more information regarding options.

files, dropping, just, into, folder, choice, your, galleries, image, gallery,

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Reffered: https://wordpress.org/