Found an old key. What do I uset it?

Few days ago I was going through all my passwords stored in lastpass, as I was going to move them to a local password manager, and came across a stored note that said multibit, and next to it there was a long string of characters.

It took me a while to realise that this had something to do with bitcoin.

A long time ago, more then 10 years ago, I played around with bitcoin. I had a wallet - multibit, and I did some little mining. Very small. But I did some.

Overtime, I ditched it, and completely forgot about it.

Right now, I know next to nothing about bitcoin and wallets.

What I want to know is, can I gain back access to the bitcoin? I'm assuming the string I stored was the key.

How do I do this? Just install a random wallet and enter the key?

What wallet should I use? I'm on a mac.

I'm very curios to find out if I still have something there. Even though I did some very small mining, back in 2011, bitcoin was worth like $0.70. Today it's worth more then $20 0000. It's worth a look.

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Edit. Correction.

The title is also suppose to be: "Found an old key. What do I do with it?"