Fixing a maternity dress

How simple is it to bring a dress in to make it tighter? I ordered a dress for my baby shower but I don’t think I can return it and get another one before my baby shower is here. I read the reviews before hand (like a week or two ago) but forgot when ordering that it ran big.

Most of the reviews are saying ordering 1-2 sizes smaller or it’s really loose. There was a couple of reviews that recommending ordering smaller but it might be tight on the arms( long sleeve). I ordered a XL which is usually my size in dresses, I usually wear xxl in shirts though.

Now I’m worried. I can do a basic stitch like when repairing a rip/hole but beyond that I’m not sure. I don’t want to mess up my dress. I’m gonna head to YouTube I was just wondering.