Above the piano keyboard you'll see a selection of icons representing the available editing tools. If you let the cursor hover over any of these you'll see a tooltip appear that tells you what it does. In most cases clicking on one of these will either show or hide a palette of tools: the notes/rests palette, or the chords palette, bar line choices, etc. The tool palettes are transparent and can be dragged around on the screen. They can also be closed by clicking their close box, and then opened again by choosing the appropriate tool icon in the toolbar.
Here, for example, is the action tools palette, which is represented in the toolbar by a pair of tied notes. It shows that the default stem direction is currently up, and offers tools to beam, tie, slur, triplet, or tuplet selected notes.
The Info button brings up options affecting the keyboard display, including MIDI options.
The Text tool gives you a text cursor that when clicked in the music will let you create a block of draggablel text.
Meters, keys, clefs, notes and rests, accidentals, misc symbols all produce floating tool palettes from which you can choose various symbols to enter in the music.
Many of these tools perform actions on selected items. For example, if you select a treble clef in your music and click on the bass clef tool that will change the selected clef to a bass clef (and redraw the music as appropriate). The one marked "tools" includes slurs, ties, triplets, stem direction - any of which can be used to change selected items in the music.
Some tools may include an "auto" button - for example, the bar line tool's "auto" button, if present, will automatically bar the entire score - an action that in older versions of Counterpointer was performed by a menu command in the Score menu. Autobar always assumes the first note or rest is the downbeat: if you want to autobar a piece with an incomplete first measure just put the first bar line in manually before using Autobar.
The keyboard octave control shifts the keyboard pitch up or down by octaves; the default "C4" setting means that middle C (C4, the fourth octave of C, midway between the treble and bass clefs) is about in the middle of the keyboard. C4 is marked with a dot on the piano keys so you can tell when it has changed.
The slider to the right of the keyboard octave control is the Zoom slider - use it to zoom in or out on your view of the music. This does not change the scaling of a printed page - it just lets you zoom in for a closer look. Scaling of a printed page is set in the Score Options window (double-click the music to see it) - print scaling affects the size of music on a printed page: e.g. 50% if you want many notes on a line, or perhaps 120% if you want to see fewer and larger notes.
The rightmost up/down arrow simply raises or lowers the keyboard window.