Do you have toddlers local-0.31 installed?
if so just replace the sms file in local/emulators/smsplus, with sms_sdl and rename it sms and your good to go!
if not go into local/dmenu/themes/base/ and edit the menu_emulators.cfg, with notepad++
Icon = "res/emulators/smsplus.png"
Name = " SMSPlus"
Executable = "./sms_sdl"
WorkDir = "/usr/local/emulators/smsplus"
Selector = yes
Thats how my cfg looks, and remember if you use other themes you must change the menu_emulators.cfg file in each theme folder.
Hope this helps!