Installed clutch kit and now wont go into gear

It sounds like the clutch is not disengaging when depressed. What is the year make and model? It most likely has a hydraulic clutch. Many vehicles have the clutch slave cylinder inside the bell housing of the transmission. This means that the fluid line to the slave cylinder was removed to remove the transmission. If a new slave cylinder was installed when the clutch was replaced (this is a good idea to do when servicing a clutch with a bell housing internal slave cylinder) then the system will need to be bled to remove air from the system and allow the clutch disengagement to function properly.

So you installed a new transmission and a whole new clutch kit? Did the kit include the pressure plate, clutch, throw out bearing and slave cylinder? Did you bleed the slave cylinder? The low and soft pedal is a clear sign that there is air in the hydraulic system. The loud noise after that tells me you're either grinding the gear trying to shift or there is a problem inside the transmission itself. If you installed everything correctly and torqued all the bolts correctly in the clutch assembly and transmission, then try bleeding the slave cylinder again, sometimes air gets trapped in the cylinder and it's hard to get out, If you let the clutch master cylinder run dry while you either had the clutch apart or while you were bleeding the clutch, then you have to start from scratch and re-bleed the whole system.

Bad transmission

You might want to check throw out bearing and pressure plate, could be out of adjustment or not matched to clutch plate

alpst sounds like your clutch disc is in backwards, DO you have a good strong clutch pedal feel?

Check the hydraulic clutch operation. This is a clutch master cylinder with a reservoir on the firewall, and a clutch slave cylinder down on the bell housing of the transmission, with a steel tube running from the master to the slave cylinder. When clutch pedal is depressed, hydraulic fluid (brake fluid) is forced from the master to the slave. The slave cylinder should push out a little plunger that contacts the clutch fork lever-pushing it forward to engage the clutch.
Add brake fluid to the reservoir if needed. Watch the plunger on the slave cylinder: if it moves little, or not enough, try bleeding the slave from the bleeder valve. They are bled just like brakes. If bleeding doesn't help, your clutch master or the slave may need replacing. The master cylinder, like a brake master, has internal seals that hold hydraulic pressure, so force can be applied to the plunger on the slave cylinder.

You might have somebody press the pedal as you get down and check the clutch travel. Might have an adjustment on the clutch arm.
Could have wrong pressure plate, did you match them. I would check the travel first.

Clutch kit problem. Check pressure plate and release bearing.

Did you take all the adjustment out that the mechanic adjusted into the push rod? With a new master cylinder, it may be adjusted so far out that the clutch is always disengaged. Try adjusting the push rod back to its initial setting.

are you sure u bled the clutch properly ? cant be any air in the line ! check fluid level in master cylinder and pull guts out of slave cylinder 2 make sure there are no leaks ( splits in the rubber ) other than that ur clutch fork may not be on the thrust bearing correctly !!!