Writing a sum in texmacs


This is a basic question but I swear I tried to read the manual about this several times before.
I can’t find a way to write correctly a sum in Texmacs. I mean that I’d like to write a capital sigma with the first index of my sum at the bottom of it and the last index at the top of it.
Instead, i use exponents and subscripts and I only get a subscript that is not at the bottom but at the right bottom of the sigma symbol.
Again, I apologize for posting such a basic request but I’m searching a way for months.
Thanks by advance, Raphaël.

apriori if your equation is in “display” mode, the sum have indexes on top and bottom, while if it is “inline” the the indexes are on the side. Usually there is not enough space on the line to allow for having indexes above and below in inline mode.

If you insist to have indexes above and below use “Insert -> Script -> Above / Below” while you select the sum symbol.

It may be that @raphaelS is using a capital sigma
@raphaelS: did you try inserting a summation symbol from the menu or with the key combination shift+F5 followed by shift+s?
If you already did, then @mgubi suggestion is the right one