Hi,

When you finish typing what you want tap the return key on the onscreen keyboard, the keyboard should disappear from the screen

Here is a picture of of just one place it might be. It can depend on the app. In this instance it is the return arrow key right most key, 3rd row down. In other apps it may also be known as enter, go, search, magnifying glass symbol or even a smiley face it depends on the app. Its' location also varies, sometimes it is on the bottom row, or even the second row up from the bottom. Invariably though it is always on the right hand side of the keyboard and mostly the key size is double the size of the letter keys.