note input mode: hold 1/4 note while playing 1/8 notes

In note input mode, on my right hand (treble clef) I'm trying to hold an 1/4 note while playing two 1/8 notes with the same hand. How do I input this scenario? It doesn't appear to allow an 1/8 note to be played at the same time as a 1/4? Or am I missing something? Hope this makes sense. Thanks in advance.