triplets & tuplets

Greetings from Colorado.
I purchased the attached score and scanned it, uploading to Musescore.
The purchased copy include triplet notation in the first measure that did not come through when uploaded. The first of three triplets in measure one begins with an 8th note rest, followed by two 8th notes, G & A. Two triplets follow that one, 8th notes B, D, & C, then C, E, & D.
I have attempted to add the triplet notations to the score according to the instructions in the manual, but when I do the score changes.
I selected the note entry icon, then highlighted the third 8th note in measure 1, then pressed CTL + 3 to start the triplet. The note values change and rests are added.
What am I doing wrong?
- John