I am making a dress for myself. I am almost finished, but I do not understand how to sew in the side insert pieces. Unfortunately, the pattern is not helpful, so any advice would be appreciated.

image _Indian blue Dress - I purchased the pattern

I don’t have the pattern but it looks like there’s a front and back that are fairly straight rectangles. The sleeves are seamed at the shoulders and for some length down the front and back and then the side seam is sewn for a few inches.
There are the two side inserts which look like long rectangles. If you fold one in half the halfway point is lined up with the side seam and then the sides of the rectangle are seamed to the front and to the back. Do the same on the second side. For this to work the length of the side rectangles has to match up to the front and back lengths that are left after the short underarm seam.
You might also try contacting the designer. Since this is a paid pattern there’s some obligation to help out with missing directions.

Also, in case you’re stuck on how to seam, generally, look for my videos called “Mattress stitch” (seaming along the side of a column of stitches) and “Kitchener Stitch” (seaming between rows) which are two common seaming methods. I believe both are on the Free Videos/Tips page here on this site.

That’s a beautiful dress, by the way!