How to apply cheats on xp

for those who have played half life 1, i have cleared zen area without applying any cheats but now it seems impossible to carry on without them as i just have 20 life left and have huge jumps to make and on each jump i lose 5-6 points and by the time i want to reach the rock which will take me to the next round…my player is dead…been trying for 5 days but no luck…
i have cheats patch and stuff…just cant apply as they say…i can post the cheats if u wish?