I want to understand how to post t accounts correctly

A T-account has 3 sides, the Top of the T, The Left side of the T, and the right side of the T.
The top of the T is for the Account Title.
The Left side of the T is for the account Debits.
The Right side of the T is for the account Credits.
The T account is used to post transcations. For example is you receive cash from a customer on account you will have 2 T accounts. The Cash T account will have a Debit posting for the amount received along with the date, and the A/R T account will have a Credit posting for the amount paid along with a date.

T accounts are used to ensure you have a Debit and a Credit posting that are equal. Also T accounts are a good tool for visualizing your transactions in order to verify your debit and credit postings.