What does it means "to use an ice cream"? [duplicate]

The phrase, is an idiom and is informal in use. According the Cambridge Dictionary,

used to say that you would like something:

Examples:

• I could use some help putting these decorations up if you're not too busy.
• "Can I get you anything?" "Thanks. I could use a drink." ​

used to say that something or someone needs something:

Examples:

• Their website could use an upgrade.
• He could use a new suit for work.

In the phrase, "I could really use a drink," the speaker means to say that he/she really wants to have a drink. You cannot say "using drink" for this purpose.

Note: This is applicable to both British and American English. Only that in AmE, it is not considered informal.

It's an idiom. Here, it means the person needs or wants a drink (probably alcoholic beverages)

Could use — Cambridge

(also could do with)

to need or want something

"I could use some help over here!"
"You could do with a haircut."