これ
「これ」means “this” and points to the item near the speaker in 「これを使ってもいいですか。」. It commonly comes before 「を」 when it is the thing being acted on. You can use it when asking permission to use or take a nearby item.
を
「を」marks 「これ」 as the object of the action in 「これを使ってもいいですか。」. It follows the thing that is used, seen, tried, or received. Use it after the object when asking about an action with that object.
使って
「使って」means “use” in 「これを使ってもいいですか。」 and is the form that connects 「使う」 to the permission pattern used in the dialogue. It follows the object marked by 「を」 here. Use this form when asking whether you may use something.
も
「も」is part of the permission pattern in 「使ってもいいですか」, where the action is presented as acceptable. It comes after the action form and before 「いいですか」. The same pattern is used in the dialogue with actions such as sitting, entering, seeing, trying, and receiving.
いい
「いい」means “okay” or “allowed” in 「使ってもいいですか。」. Together with the preceding action form and following polite question ending, it asks whether that action is acceptable. Use it in this permission question pattern when you want to ask if an action is permitted.
です
「です」adds a polite sentence ending to 「いいですか。」 in each permission question in the dialogue. It follows 「いい」 here and helps make the question polite. Use this polite ending when asking permission in a respectful everyday conversation.
か
「か」marks 「いいですか。」 as a question. It comes at the end of the polite permission questions in the dialogue. Use it at the end when you want the listener to answer whether something is allowed.
ここ
「ここ」means “here” and identifies the place in 「ここに座ってもいいですか。」. It is followed by 「に」 to show the place where the action happens. Use it when asking about doing something at the speaker’s current location.
に
「に」marks 「ここ」 as the place where the speaker will sit in 「ここに座ってもいいですか。」. It follows a place expression such as 「ここ」. Use it before a movement or position-related action when identifying a destination or location.
座って
「座って」means “sit” in 「ここに座ってもいいですか。」 and is the form connected to the permission pattern in the dialogue. It follows the place marked by 「に」 here. Use this form when asking whether you may sit in a particular place.
入って
「入って」means “enter” or “come in” in 「入ってもいいですか。」 and connects 「入る」 to the permission pattern. No place is stated in this line, so the location is understood from the situation. Use it when asking permission to enter a room or another space.
それ
「それ」means “that” or “it” and refers to an item already identifiable to both speakers in 「それを見てもいいですか。」 and 「それを試してもいいですか。」. It comes before 「を」 when it is the object of the action. Use it when pointing to something that is not being introduced as 「これ」 in the conversation.
見て
「見て」means “see” or “look at” in 「それを見てもいいですか。」 and connects 「見る」 to the permission pattern. It follows the object marked by 「を」 here. Use it when asking permission to look at something.
試して
「試して」means “try” in 「それを試してもいいですか。」 and connects 「試す」 to the permission pattern. It follows the object marked by 「を」 here. Use it when asking permission to try an item, method, or activity.
もらって
「もらって」means “receive” or “have” in 「これをもらってもいいですか。」 and connects 「もらう」 to the permission pattern. The object being received is 「これ」, marked by 「を」. Use it when politely asking whether you may take or receive something.