The accounting is divided into periods of time known as fiscal years. Fiscal years often but not always correspond to calendar years. Add a fiscal year using the '+' button below the list of fiscal years. Specify a name (which can be anything) and start- and end dates. The fiscal year includes the end date.
For each fiscal year you add, folders are created under 'Entries' and 'Invoices' in the sidebar. If you have many years you can check the box 'Don't show' for older years. They will no longer be shown in the sidebar.
For each fiscal year except the first one you should add starting balances for all accounts in the balance sheet (assets, debt and equity). Starting balances are shown in the table at the bottom right. Click '+' below the table to add a balance. Note that balances for debt and equity should normally include a minus sign, so that the sum of all starting balances is zero. The current sum is shown next to the table.
Economacs can automatically calculate the starting balances based on the ending balances of the previous fiscal year. Click 'Calculate from previous fiscal year' to do this. This will replace all previously defined starting balances, which means that it is safe to do this repeatedly. If you add or change entries in the previous fiscal year, don't forget to update the starting balances.
Before you calculate the starting balances, make sure that you've created an entry (in the previous fiscal year) that transfers the profit or loss from the profit/loss sheet to the balance sheet. You can find more information on what this entry should look like in a book on accounting.