Tungnath is the highest shiva temple of Uttarakhand and is situated at the altitude of around 12000 ft from sea level just below chandrashila peak which is at an altitude of around 13500 ft from sea level. Its an easy 3 km long trek from chopta which can be easily completed in 2-3 hours.
If you are planning to reach through public transport you will have to switch busses at a few point which I'll be mentioning below. (Assuming you are traveling from Delhi)
Delhi - Haridwar
Haridwar - Roodraprayag
Roodraprayag - Ukhimath
Ukhimath - Chopta
Even if you are going through your own vehicle you can use the Google maps or just follow the same path I.e. going through same points or locations.