How to enable blocking mode:
Turn your android ON and go into Apps or open settings.
Press the left side just beside the home button on the bottom of your screen
If you find it difficult, select Apps from your home screen
Now you need to look for Settings icon. Depending upon the number of applications installed it will be on some screen. Just swipe the screens until you find Settings App
Now under settings you have number of other tabs and information.
Under device from the top bar and below you will find Blocking Mode.
Press the blocking mode and you will enter into blocking mode. Here you can manage different settings like block incoming calls or setup a time when the blocking mode will enter automatically into blocking state. This is very useful specially if you have meetings on daily/ weekly at a same time.
As you see from the above screen everything is grayed out, as this make sense since we did not enable it yet. On the Top left of the screen just besides Blocking mode swipe the circle to right and this will in turn enable the blocking mode.
You can also customaries this, for example say if you want to receive certain calls you just need to add the contacts. To do this just select allowed contacts from the bottom of the screen in above screen shot and a pop up window will appear with different options.
None: No contacts
All contacts: those contacts available on your phone
Favorites: These are your contacts which you have marked as favorite in your contact list
Custom contact: specific contact from contact list.
Select whichever is applicable in your case and you are done with it.
Please note Blocking mode is enabled as soon as you enable this feature and needs to manually turn it OFF unless you did not provide any specific time frame.