Sony xz unknown sources

[Lizzie1976]

Hi, i put an app on my phone that required me to tap the "unknown sources button" the link took me directly to this, so it was easy to find. But now I am unable to find it to turn it back off again. I have been to settings, security /lock screen settings and it just is not there. I have watched numerous YouTube videos and they all say it should be there, but it isn't. Please can you advise? 

[Uliwooly]

@Lizzie1976 

Go to:

Settings > apps & notifications > Advanced > Special app access Install unknown apps > select the app 

[Lizzie1976]

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@uliwooly wrote:

@Lizzie1976 

Go to:

Settings > apps & notifications > Advanced > Special app access Install unknown apps > select the app 

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Hi, 

This unfortunately is not what I wanted. What I want is to disable Allow unknown sources. I have attached a link on how to enable on my phone. But the button isn't there on my phone. 

https://youtu.be/Lx_qBxfm_EQ