Changing needles?

I’m pretty new to knitting and I’ve been improvising a pattern with this very nice yarn I was given. It’s 2 ply yarn and I was trying to have make a decreasing/ triangle-ish pattern. I started on size 4 needles, but want to decrease it down to 3s since the weave is kinda loose.

Is there a special way to do this or should one row just start with 3s? I’m knitting in Stockinette stitch if that helps!

Thanks!

The easiest way to change needles is to knit (or purl) onto the new size needle. There’ll be a change in the gauge but hopefully it won’t be too noticeable. If you could change at a point where there is a change in the stitch pattern it would hide the change.