Blogger detailed instructions:

Basically first you'll need to activate the Blogger API.
Once it's activated you'll need to create your 'Client ID' (aka App) which will auto post on your behalf.
We provide detailed instructions below.

Please go at this url: https://console.developers.google.com/

Then find 'Blogger API' and click on it to activate.

At this point you might need to create a project before being able to activate API.

Once the project is created you can enable the Blogger API.

Once you activated the Blogger API v3, you need to create your 'Client ID'.
On the left side select 'Credentials'

Then click on 'Create credentials' and select 'OAuth client ID'

At this point you might need to configure 'Consent Screen'

Please enter 'Email Address' and 'Product name' and click Save

Finally you're able to create Client ID.
For 'Application type', select 'Web application'.
For 'Authorized Javascript Origins', enter your blog url (ex: http://www.yourblog.com)
For 'Authorized Redirect Uri', enter the Url when you're on the settings of MicroblogPoster.
It is something like http://www.yourblog.com/wp-admin/options-general.php?page=microblogposter.php
Click 'Create'.

Copy the Client ID and Client secret and configure your account under MicroblogPoster.

MicroblogPoster will provide you a link in order to authorize the App posting on your behalf.