first you need to reach student 1 on your character and unlock all the three companions through main quest line.

the important thing to do is to keep your beginners orders during the walkthrough.
once you got all your companions and all the quest beginner orders, just level up to 50 with beginner orders only your second female companion Li Lingshuang, not the first one (Yilang).
if you still have beginners orders, use them on Yilang next.
You should end with a companion lvl 50 and the second one around 25-26.

Make sure to use orders that works for lvl 50-65 only on a lvl 50 or 50+ character. You can waste those more rare orders on a inferior to 50 character if you are not careful so take care.

so now you have at least 1 lvl 50 + another one more than 20.

You need to head to Frozen Path dungeon on easiest difficulty, and repeat it with your two highest level companion.
Just spam it and youll get between 15 and 20 orders each run.

It took me 2 hours 20 minutes to get the three at lvl 50.

The location of instance is in Weichuan Highlands, the screenshot shows where it is (my pointer)

its not of a big deal but i'd advice keep your orders you got from main quest that make you able to lvl up 50+ ( you receive only a few) till you have all your three companions lvl 50 with the use of only beginner orders.

Once you there, try to optimize how to use the highest rank orders on your two favorite companions to get them lvl 51 and 51, or 52 50, or 52 51 for example, use them 1 by one to not waste half a level on your companion exp, as that you will optimize the strenght they have.

You can also do that qui effectively once you reached lvl 33 in main quest and got a 40+ and 25 companion but will be quite slower