The ta-form: past and completion
The ta-form commonly describes past events, but its role changes in larger patterns. Separate how the form is built from the time reference of the whole sentence.
Build on the te-form
If you know the te-form, change て to た and で to だ: 書いて → 書いた, 読んで → 読んだ, 食べて → 食べた. Preserve the distinction between voiced and unvoiced endings.
行く becomes 行った, する becomes した, and 来る becomes 来た（きた）. Checking the verb group first helps you avoid forms such as 帰た for the group 1 verb 帰る.
Past events in a main clause
昨日、映画を見た。 means 'I watched a movie yesterday.' 見ました makes it polite. 見た and 見ました differ in politeness, but both describe the same past event in this sentence.
The negative past is 見なかった. Do not attach た directly to ない to make 見ないた. Practice affirmative and negative past forms together so that small differences at the end remain noticeable.
Interpret the following pattern
食べたあとで出かけます。 means 'I will go out after eating.' It can describe a future plan before the meal has happened: the ta-form marks eating as completed before going out.
行ったことがあります expresses experience, while 行ったほうがいいです gives advice. Do not interpret every occurrence of た as 'already went'; check the meaning created by the complete expression.
Check: Does 食べた in 明日は食べたあとで出かけます。 mean that the meal was eaten yesterday?
Show the answer and why
No. It describes going out tomorrow after finishing a meal. The whole sentence is a future plan, and た marks completion before the later action.