How to save the text box values into an array?

I would use a separate counter variable to redefine the size of the array, like this:

Option Explicit

Dim myArr() As String  '~~~ dynamic array
Dim lngCnt As Long     '~~~ a counter variable that keep track of the index

' inital stage..
Private Sub Form_Load()
    lngCnt = 0
End Sub

' on KeyPress
Private Sub Text1_KeyPress(KeyAscii As Integer)
    If KeyAscii = 13 Then   '~~~ if Enter Key is pressed..
        ReDim Preserve myArr(lngCnt)    '~~~ reclare the array with the new size, while preserving any elements it may contain
        myArr(lngCnt) = Text1.Text      '~~~ store the line
        Text1.Text = ""     '~~~ empty the textbox, so that you could type the next line

        lngCnt = lngCnt + 1 '~~~ increment the counter, which we would use as size during the next keypress
    End If
End Sub

' to display the elements
Private Sub Command1_Click()
    Dim i As Long

    For i = LBound(myArr) To UBound(myArr)  '~~~ loop through the elements(from Lowerbound to Upperbound)..
        Debug.Print myArr(i)                '~~~ ..and display the item.
    Next
End Sub