You can easily change the the hud of dooruse or use this:
it use the fpgcraw commands to create a text line
;Artificial Intelligence Script
;Header
desc = Use Door (Push Open and Push Closed)
;Triggers
;keypressed=33 1 : F is pressed
;keypressed=18 1 : E is pressed
:state=0:state=10
;change here the fpgcrawtest="What you want to read ingame"
:state=10,plrdistwithin=60:fpgcrawtext=Press F to open door,fpgcrawtextsize=36,fpgcrawtextfont=Arial Black,fpgcrawtextr=255,fpgcrawtextg=255,fpgcrawtextb=255,fpgcrawtextx=50,fpgcrawtexty=70
;keypressed="key code" 1
:state=10,plrdistwithin=60,keypressed=33 1:state=1,setframe=0,sound=$0
:state=1:incframe=0
:state=1,frameatend=0:state=2,coloff
;keypressed="key code" 1
:state=2,plrdistwithin=60,keypressed=33 1:state=3,sound=$1,colon
:state=3:decframe=0
:state=3,frameatstart=0:state=10,setframe=0
;End of Script