First, I welcome you to the forum. Typically, if you are going to stamp any pattern on Veg Tan leather you are going to cut it with a 'knife.' Now, in the since of what we think of a knife, some of this is true for this job. The knife commonly referred to as a swivel knife (because the barrel can rotate 360 degrees for turns) is used to cut a channel in the leather. Now the school of thought is that you typically want cut down to a depth of 1/2 the thickness of the leather. With this cut line, you can now use stamping tools to add depth and effects.
To put this into perspective, think of the swivel knife as a pencil when drawing something. The pen will provide you a foundation and the shading and other items will add to your picture. Now, you can stamp without the swivel knife, but your lines will hard to follow. Take a look around the forum and you will find some pictures to show you what I mean.
If you have a chance, purchase the 'leather working manual' at Tandy. It is the best (IMHO) beginners book to help you understand this thing we call 'leather craft!'
Good question!