https://www.linuxjournal.com/content/copy-and-paste-screen
Enter Copy Mode
The first step is to enter copy mode from within Screen. Press Ctrl-a-[ to enter copy mode. Once you're in this mode, you can use arrow keys or vi-style keybindings to navigate up and down your terminal window. This is handy if you are viewing a log or other data that has scrolled off the screen and you want to see it. Typically people who are familiar with copy mode just use it for scrolling and then press q to exit that mode, but once you are in copy mode, you also can move the cursor to an area you want to copy. Copy Text
To copy text once in copy mode, move your cursor to where you want to start to copy and then press the space bar. This will start the text selection, and you'll see the cursor change so that it highlights the text as you then move the cursor to select everything you want to copy. Once you are done selecting text, press the space bar again, and it will be copied to Screen's copy buffer. Once text is copied to Screen's clipboard, it automatically will exit copy mode. Paste Text
Once you have text in the copy buffer, you can switch to a different Screen window, open a text document in your terminal or otherwise move the cursor to where you want to paste. When you are ready to paste, press Ctrl-a ] (note that this is the opposite bracket from what you use in copy mode) to paste. As with other clipboards, you can paste multiple times as needed.
To open a new window, press Ctrl+A, release, and then press c. This creates a new window on top of your existing window.
To create a horizontal split, press Ctrl+A and then S (not?? isit the uppercase). This places one window above another, just like window panes. The split space is, however, left unpurposed until you tell it what to display. So after creating a split, you can move into the split pane with Ctrl+A and then Tab.