How to Add Existing Account to Ps4?

Using an Existing Account

Select (Settings) > [Start] > [PlayStation™Network] > [Sign Up]. If you are already signed up on your system, [Sign Up] is not displayed. Select [Use an Existing Account]. Enter the sign-in ID and password for the account created on a different device and select [Next].

Can I Login to my PS4 Account on Another PS4?

Yes you can. You could even download your owned games and saved dataps+ membership on another ps4 while logged in. However you cannot log into two or more PS4 consoles at the same time with same PSN account .

How do I Link my PS4 Account to my PS4?

Select Account Management. Start Settings and then go to Account Management.
Select Activate as Your Primary PS4. Choose "Activate as Your Primary PS4" to allow users on this console to play your games.
Confirm this choice by selecting Activate. Be sure to choose "Activate" to finish the setup process.

Can I Merge 2 PS4 Accounts?

No. Accounts can be deleted, an account can be registered on multiple PS4s, and multiple accounts can be registered on one PS4, but they cannot be merged. All games and services purchased are exclusive to the account in question, minus any intended local game sharing features.