Passing on knowledge about software development and other related technologies.
It's really easy since the advent of Android 4.0 and later...
First, to cut or copy any text, keep the particular text pressed for a while until you see some options appearing on screen (this is called a long press) that include copy, select all, cut and others. Choose “Copy” or “Cut”, whichever you require to use and head to the text box where you want this copied text to be pasted.
To paste that text you copied earlier, long press the text box until again you see the options showing on screen. You will find a “Paste” option in all the listed options. When you choose paste, the copied text will be pasted in the text box.