To sew clothes in Engpsh, you can say:

"I'm going to sew a dress."
"I'm going to sew a button back onto my shirt."
"I'm going to mend a hole in my jeans."
"I'm going to alter this shirt to fit me better."

Sewing can also be referred to as "stitching" or "tailoring."

Here are some other phrases you might use when discussing sewing clothes:

"I need to buy some thread and a needle to sew this."
"I'm using a sewing machine to speed up the process."
"I'm not very good at sewing, so I'm taking it slow."
"I learned how to sew from my grandmother."

I hope this helps! Let me know if you have any other questions.