Hi @[deleted], based on what you've described, you can easily do this by first selecting your desired key and time signature from the right menu bar. Upon clicking, simply hover your mouse to the start of the project/piece.
Once you've set your desired time and key signature, you may choose from any of the note/rest values which can be found on the left tool bar, then place it on the staff, depending on the pitch you want.
If you want to do triplets, place first the three eighth notes you want to form into a triplet. Once the three notes are in place, select the triplet button (still on the left toolbar) then click on the note you want to set as the first note in your triplet.
You may refer to the attached screenshot.
