There is no "settings" menu !!
Goto >Last icon (profile), looks like a person image
scroll to bottom > select settings
scroll and select signature
under that it'll show u all the forums that u've added
select Traderji.com
option 1
disable for forum post
option 2
disable for forum PM
u can turn both off.
If u want to promote Tapatalk, just select "Sent using Moto XYZ using Tapatalk"...
then just edit the line to whatever you like.