Open a dedicated bank account in the entity's exact legal name.
Separates business and personal money — required for clean books and for many tradelines/cards.
Bring your formation documents and EIN letter to a bank or credit union.
Source: Your chosen bank / credit union
Free to open at most credit unions; some banks charge a monthly fee below a balance minimum
Reported on-time payments are the raw material of a business credit file. Tradelines that don't report do nothing.
This is general business-credit education, not financial, legal, or tax advice. Confirm specifics with a licensed professional and the official sources directly.