Okay, let’s go step by step on this one. You are saying that you want to record your investment into this company as equity? Right?.
Is it one of the following:
You are putting in Money in form of check or cash or wire. Which hits your bank or cash account. So your first step would be to create a bank account or a cash account or use or modify an existing one. To do this go to Home>Accounts>Chart of Accounts, expand on Assets>Current Assets and see you’d like to create a new cash/bank account or use or modify an existing one. For modifying, click on the account and hit Edit. In the ensuing screen modify the values as appropriate.
Now go to base tree on Chart of Accounts and Expand Equity. Now you can use an appropriate account, say Capital Stock.
Now go back to the journal entry, pick the Equity account on the credit side and debit the Bank/Cssh account. Enter the amount. Save submit!
You have already spent money on the business and you are just recording it. Go to the Assets branch on the CoA and Temporary Accounts branch. Now use the Temporary Opening account or create a suitable one and use that in lieu of the Cash/Bank account in the preceding paragraph.
While ERPNext is easy to use, it has to work with the accounting standards for each country. Suggest you Google for an appropriate Accounting Entries site for your country and follow along the suggestions that site or page makes for various things.
Sometime into the future when you are ready to confront your accountant, you can ask her/him to help you with the balance amount in the temporary account.
Hope this helps.