Where is the § button on dell inspiron 1545 laptop

That is not a standard symbol that is found on a keyboard.

If you need to use that symbol you can go into Character Map and select from there. The faster way to do it is by looking at the Keystroke code shown in the bottom right corner of Character Map.

It should say ALT+0167. That means press down and hold the ALT key while typing in 0167 on the number pad; NumLk needs to be on. That will not work with the row of numbers about the letters, you must use the number pad.