How can I output each letter of a prewritten word on a new line?

The task is to write an exe program (16 bit) that will display a prerecorded string (we use variables) in the following order. In the first line 1 letter from the line, in the second 2, in the third 3, etc. to the last character in the variable string.

Can anyone help as I don't understand this assembler at all((

That's all I'm capable of:

.MODEL TINY
.STACK 100h 


code:
    xor cx, cx
    mov cl, 5   
@1: mov dx, mess1
    add dx, cx
    mov ah, 9
    int 21h 
    
    mov dx, offset crlf
    mov ah, 9
    int 21h
    
    sub cx, 1               
    cmp cl, 0              
    jg @1
    mov ah,04Ch             
    mov al,1h
    int 21h  
    
    mess1 db "Artem$"
    crlf db 10, 13, "$"

end code    

You will need two DOS functions: AH=9 WRITE $-TEMINATED STRING TO STANDARD OUTPUT
and AH=2 WRITE CHARACTER FROM DL TO STANDARD OUTPUT. Let's load one character to DL, print it using INT21h/AH=2, then print the string crlf using INT21h/AH=9 and repeat in the loop CX times.

code:               ; Let CX keep the number of characters in mess1.
    xor cx, cx
    mov cl, 5       ; OK, but it's shorter to use mov cx,5 instead.

This is wrong, we need the register DL for other purpose.

;    @1:mov dx, mess1 
;        add dx, cx
;        mov ah, 9
;        int 21h 

Let's use other register to keep the address of each character, preferably register SI:

    mov si, offset mess1

The main loop starts here:

@1:     mov dl,[si]  ; Load one character to DL.        
        inc si       ; Prepare the address of the next character.
        mov ah,2     ; Print the character from DL. 
        int 21h

Now it's time to print crlf as a string:

    mov dx,offset crlf
    mov ah,9
    int 21h

Loop to print the remaining characters. SI points to the next character, CX is the loop counter.

    sub cx, 1               
    cmp cl, 0              
    jg @1

This could work but more elegant is loop @1 or

    dec cx
    jnz @1

All five characters were printed on new lines. Now it's time to terminate the program.

    mov ah,04Ch             
    mov al,1h
    int 21h  

.MODEL TINY produces DOS COM program which may be alternatively terminated with a simple instruction ret.