Hi sgt sax, welcome to the forum! You can input hairpins anywhere by using the caret (the orange line you use to input notes) - select the whole note, press Shift-N to show the caret, then move the caret to halfway along the note (e.g. press 7 to select the half note duration, then press Space to advance by a half note). Press < to start a hairpin, then press Space again to advance the caret and extend the hairpin. Then press Esc when you’re happy.
Alternatively, if you have shorter notes already elsewhere, you can select notes that last for a half note together, add a hairpin to them, then copy it to where you want by selecting the hairpin and Alt-clicking wherever you want to paste it.