Start a journal

by hand

(power users)

The simplest possible journal is just an empty file:
echo >2017.journal

The name doesn't matter much and can be changed later. One file per year is common, and so is a .journal or .hledger extension.

Record a transaction, using journal format:

$ cat >>2017.journal
2017/1/26
  expenses:food     $10
  assets:cash
<CTRL-D>

Account names can be anything and you can change them later by search and replace. If you don't know what to choose, start with these five:
expenses, income, assets, liabilities, and equity,
perhaps with one extra subcategory as above.

by text editor

Write transactions in a text editor and save the file.

by add

Use the add command:
hledger add -f 2017.journal
enter one or more transactions

set LEDGER_FILE

To avoid typing -f FILE every time, set the LEDGER_FILE environment variable. Eg:
echo "export LEDGER_FILE=~/finance/2017.journal" >> ~/.bash_profile && source ~/.bash_profile

Most examples here assume you have done this.

by hledger-iadd

ensure $LEDGER_FILE exists
hledger iadd
enter one or more transactions

by hledger-web

ensure $LEDGER_FILE exists
hledger web
wait for web browser to open
click "add transaction" or press "a"
enter a transaction, click ok or press enter