1) Go to developers.facebook.com and click on Log In in the top right. Log in using your personal Facebook account.
Note: You must use the username and password from your personal Facebook profile. Facebook doesn’t allow businesses to register as developers, only individuals.
2) If this is your first time signing in to the Facebook Developer portal then click on Register. Registering is a quick an easy process which will take less than a couple of minutes. If you’re already registered then you can skip ahead.
3) Hover over Log in and Click Add New App.
4) Enter App Dsiplay name and Click on Create App ID. Then Click on the "Im not Robot or if it asked for capcha, provide correct capcha.
5) Then, go to the Settings > Basic to get your app information and Fill in the fields.
6)Provide Facebook Account password to confirm if asked and click Submit
7)Now from the Menu hover over Tools and Click on VIEW ALL TOOLS
8) On the next page Click on Access Tool Token
9) You need to Give permission to the app you have just created to create Access Token. Click on need to grant permission link
Important: Leave the app in Development mode. Do not make it Live.
10) Click Continue
11) Go to developers.facebook.com/tools/explorer/ and select the same app you set up in step 4 from the Application drop-down list show below:
12) Click the Get Token button and click Get Page Access Token.
13) Click on Continue as button to Grant permission to the app if asked.
14) Then Select the page of which you want to get Access Token from the Get Token drop-down list.
15) Copy the Access token .
16) After copying Access Token for Desired Page, Hover over Tools in the top Menu and Click on Access Token Debugger.
17) To make it Long-Lived like it will work for the longer time click on the Extend Access Token and copy the newly generated Access Token and put it in the plugin.