You can use commercial bias binding for this or create your own

  To create your own bias binding, cut 2cm wide strips of fabric on the bias (diagonally)

 Stitch them together

 Press out

 Press in half horizontally

 Stitch the two back pieces together

 Stitch one shoulder seam

 Press the seam on both sides

 Then press it out. You should do this for all seams

 Pin bias binding to neckline

 Stitch bias to to neckline

 Press seam allowance 

 Stitch bias and seam allowance

  Press bias binding under

 Stitch remaining shoulder seam and press

 Stitch side seams and press

 Finish bottom edge

 Stitch hem