If you start off with one of the Sage 50 templates you should have all the accounts you will likely need.

Sage requires a special 'X' Account that shows current year earnings 'on the fly' as transactions are entered,

The shareholder's original contribution is some sort of capital stock, which should show in the Equity section.

There will have to be a Retained Earnings account, normally this is only for the software to automatically tally net income for each year into.

Shareholder loans are recorded in the Asset or Liability section, depending on whether they are loans 'to' or 'from' the company.  For lending purposes, banks often 'reclassify' shareholder loans as equity for the purpose of evaluating whether the company meets their criteria.