I gather you're taking things in. That's pretty easy to do. One way to go is to put them on inside out, pin the old seams snugger so it looks and feels about right, then caaaaarefully remove the garment, and sew where the pins are. Just taper down what you're taking in 'til you meet the old seams somewhere they still fit. Kind of like making a dart, if you've done that. Then try it on the right way. If it's ok, then you can cut off some of the extraneous material (down to ordinary seam width), press so it doesn't bulge and zig-zag so it doesn't ravel (however that's spelled).

Oh, and if this means you've lost weight, and if that was your intention, then congratulations! Wish I could say and do the same.