How to have a home-button replacement/ assistive touch

Open settings

Go to general

Now, scroll down to Accessibility

Scroll down and hit Assistive Touch

Switch Assistive Touch to ON

Now you should be seeing a white circular ball in front of your screen

Now tap on the white circle, and you will now see a number of options to choose

From the previous step, hit device and see a number of options, like increasing/decreasing volume, mute/unmute, lock screen, etc

Again, from the previous step you can also access a number of additional features by hitting 'more' and then enjoying more options