Head back to Documentation
To check the balance of a wallet browse to the QRL Explorer and enter your address into the search field.
Enter the QRL address into the search bar in the top right of the Explorer.
You can enter QRL addresses, transaction hashes, or block indexes into this field.
This will show you the current balance and all transactions that have happened with this wallet.
At the bottom left there is a meta button. This will give fine grain details for the current wallet.
Using a terminal with qrl installed you can simply enter
qrl wallet_ls to get the balance
for more info on installing QRL see the doc here