Bonnie - no need to fix if you don't want to -
If on paper, mount (matt) and frame behind glass
On canvas, use an isolation coat of medium (gloss or matt) whichever you prefer and then if you wish
use an acrylic varnish - again, matt, gloss or satin.
On board - if behind glass, use spacers to keep the surface off the glass,
or, frame without glass and treat as canvas.
Sign either front or back - it's a personal thing!
I like my sig to be non-imposing! Often sign on the back too.
On the front, before you varnish.
Use either a fine brush (difficult) or a pen and acrylic ink (my choice).