First step when making web updates is to log into your site. Your user name and password will be provided .
DO NOT LOOSE IT

Both username and password will be the same for Login Into Nice Page also.

Once you have successfully logged into your Joomla website you will be presented with the standard Joomla UI.

The only section of any interest for your is the "Articles" section highlighted below.

Click the "Articles" tab and it will produce a list of all your "Articles/Pages" on your site

Select any "Article" and it will start the editing login process with NicePage, select "edit With NicePage" to begin.

Select "Edit with Nicepage" and you will be asked for Username and Password. Again the one supplied by SoftWEAR Systems it is the same as your Joomla login and password. Once logged in the UI will present itself.

Use the following more detail links to continue further:
Controls overview:
https://nicepage.com/doc/controls-overview-1128
Basic User Interface:
https://nicepage.com/doc/user-interface-v-0-1131
KeyBoard Shortcuts:
https://nicepage.com/doc/keyboard-shortcuts-47999

Advanced Topics:
Block Builder:
https://nicepage.com/doc/block-builder-1129
Page Builder:
https://nicepage.com/doc/page-builder-1021