There are lots of ways to create triplets. Here's the way I usually do it in Speedy Entry.

1. Press CTRL+3
2. Enter the first note as an eighth note (yes, an eighth note)
3. Then, backspace with the arrow key and change the initial eighth to a sixteenth note (Press 4 on the keypad)
4. Continue entering the notes you want.

When you press CTRL+3 in Speedy, the first note you enter sets the "denomination" of the triplet, but then you can overwrite the note's duration.

In Simple, I set my tuplet definition to 3 eighths in the space of 2 eighths.

Then, it was a simple matter to enter the first note, tap the 9 key, and enter the others. Occasionally, there was an extra 16th rest showing when I finished, but it seemed to be a visual artifact, only. As soon as I entered the first note of the next tuplet, it disappeared. I use the numberpad to set the durations: 3 for a sixteenth note, 5 for a quarter.

In Speedy:

press Opt.-1 (alt-1)  FWIW, I'm on a Mac

The tuplet definition box appears. Make sure it says "3 8ths in the space of 2 8ths" (that's mathematically what you want).

Now that the tuplet definition has been set, just enter 2 16th notes and a quarter. That should do it.