How to download iOS 13.5 software

Start here:--> Update your iPhone, iPad, or iPod touch – Apple Support

Regards

Giulio

On your iPhone screen look for settings then click on it first then click on general next then a window appears under general then look for Software Update then click on it. It will tell you your software is up to date or not? For instance for my iPhone 6+ I'm using now then my update is iOS 12.4.7 now and more updates to come for my iPhone 6+. Also, I can't update to iOS 13 because my iPhone 6+ is too old