Insula segmentation

Hi, I’m trying to perform insula segmentation by following the procedures at
I’m new to slicer, so I got stuck at the first step.
“1) On a T1 MRI image, using the Segment Editor module, we used 3 segments (via “add” icon). The first segment was for the background, the second for the whole Insula and the third for the separation between the two subunits of the insula, i.e., aINS and pINS. To establish accurately the borders of aINS and pINS we traced the Circular sulcus and the Central sulcus of the Insula as follows. First, we used three sagittal images where these sulci were visually well-identifiable. Consequently, these sulci were detected on coronal sections as a series of dots, which served as our key anatomical landmarks for the segmentation of aINS and pINS. More specifically, the circular sulcus of the insula determined the outer boarder of the insula in its entirety and the the Central sulcus (cesi) determined the for border between anterior and posterior Insula (coronal view).” I’m tring to draw the border of insula, but after I finished drawing, insula simply just got painted within the border line. Any suggestions! Thanks. Is there better way for manual segmentation