xiān bǎ xǐyīyè fàng zài wūzì shàng, zài jìnpào yīfu.

把 introduces the object before the verb and highlights what happens to that object.

Pattern: 把 + object + verb + location/result

So here:

• 把洗衣液放在污渍上 = take the laundry detergent and put it onto the stain

This structure is very common when:

• something is being moved somewhere
• something is being changed
• the speaker wants to emphasize the handling of the object

A more basic word order would be:

• 先在污渍上放洗衣液

But 把 makes the instruction sound very natural and action-focused.

Because the verb 放 means to put/place, and the thing being placed is 洗衣液.

In other words:

• 洗衣液 = the thing you move
• 污渍上 = the location where you put it

So the logic is:

• put detergent onto the stain not
• put the stain

That is why 把 introduces 洗衣液.

先...再... is a very common pattern meaning first... then...

In this sentence:

• 先 = first
• 再 = then / after that

So:

• 先把洗衣液放在污渍上
• 再浸泡衣服

means:

• first apply the detergent to the stain
• then soak the clothes

This pattern is especially common in instructions, recipes, and step-by-step explanations.

They are different characters with different meanings, even though they are pronounced the same here.

• 在 = at / in / on; used for location
• 再 = again / then / after that; used for sequence or repetition

In this sentence:

• 放在污渍上: 在 shows location
• 再浸泡衣服: 再 means then

So even though both are zài, their jobs in the sentence are completely different.

Because 放在...上 is the normal way to say put something on/onto...

Structure:

• 放在 + place + 上/里/旁边 etc.

Examples:

• 放在桌子上 = put it on the table
• 放在包里 = put it in the bag

So:

• 放在污渍上 = put it onto the stain

If you say 放污渍上, it sounds incomplete or unnatural in standard Mandarin.

上 means on or on top of.

So:

• 在污渍上 = on the stain

Chinese often uses a location word like:

• 上 = on
• 里 = in
• 下 = under

Even though a stain is not a separate physical object like a table, Chinese still naturally says 在污渍上 because the detergent is being applied onto the stained area.

Because this is an instruction, and in Chinese the subject is often omitted when it is obvious.

The understood subject is basically:

• you

So the full idea is like:

• 你先把洗衣液放在污渍上，再浸泡衣服。

But in instructions, manuals, recipes, and spoken directions, Chinese usually leaves out the subject to sound more direct and natural.

Because Chinese does not need 把 every time there is an object.

浸泡衣服 is a normal verb + object structure:

• 浸泡 = soak
• 衣服 = clothes

So:

• 再浸泡衣服 = then soak the clothes

You could say:

• 再把衣服浸泡一下

but that sounds a bit more deliberate or formal. In a simple instruction, 再浸泡衣服 is perfectly natural.

Yes. 洗衣液 means liquid laundry detergent.

Related words:

• 洗衣液 = liquid detergent
• 洗衣粉 = laundry powder / detergent powder
• 洗衣皂 = laundry soap

So if the product is liquid, 洗衣液 is the right word.

It is usually pronounced yīfu, with the second syllable in a neutral tone.

So not usually:

• yīfú

but more naturally:

• yīfu

That neutral tone is very common in everyday Mandarin.

浸泡 is common and natural in instructions, labels, and cleaning directions. It means to soak.

In very casual speech, people might also say:

• 泡一泡衣服 = soak the clothes for a bit

But for product instructions or careful directions, 浸泡 sounds very appropriate.

Yes, sometimes, but the feeling is a little different.

• 先...再... is a very neat, standard sequence: first... then...
• 然后 means then/after that and is also common

So you could say:

• 先把洗衣液放在污渍上，然后浸泡衣服。

That is also correct.

But 先...再... sounds especially good for step-by-step instructions, so it fits this sentence very well.