First thing you need to look at is your water. Liverworts are very susceptible to the types of salts in water. So it is best to use distilled or r/o water only.
Secondly, check out my recent thread on growing Marchantia.
You need to take the liverwort off of the old soil that is in the pot you purchased. Then get some sand, creek or river only and mix with some peat moss. And probably divide the clump up into 2 pots. Make a depression in the sand mix and press in the liverwort. Water and bag into a one gallon sized bag and put in a spot that gets a couple of hours of direct sun on a northern exposure. Give it time.