New clutch, will go into gears when truck is off but not when it is on

i just recently put a new clutch in my truck and when the truck is off i can move the shifter into gears but she i turn it on i press the clutch pedal and it still wont go into gear

Do you have direct clutch linkage or a hydraulic one? What is the year of the truck?

Did you adjust the clutch pedal? Even an hydraulic clutch has an adjuster. Most are under the dash for hydraulic. Also, did you try to bleed the hydraulic system?

hydraulic,the slave cylinder has fluid in it too

we didnt bleed it,im a high school student,my auto teacher told me to keep pumping the pedal to pump fluid into it but it didnt work

Unless you bleed the air out, your not helping yourself. There’s a bleed valve at the slave cylinder just for this purpose. Do you know the technique where you pump, pump, pump, hold, and bleed?

nope,i know where the reservoir for the clutch fluid is,where are you supposed to bleed it from?

Down at the slave cylinder. Where is the truck now? If you can drop a transmission and replace the clutch, you should be able to bleed the hydraulic clutch system. It is very similar to bleeding the brake system.