i want to install a gmail app on my laptop

You can set it up in Apple Mail (info from Google's Help):

Use IMAP to check Gmail on other email clients

Set up IMAP and change your SMTP settings to read Gmail messages in other mail clients, like Microsoft Outlook and Apple Mail. When you use IMAP, you can read your Gmail messages on multiple devices, and messages are synced in real time. You can also read GMail messages using POP - see below (though IMAP is probably better).

Note: To avoid temporarily locking yourself out of your account, make sure you don't exceed 2500 MB per day for IMAP downloads and 500 MB per day for IMAP uploads. If you're setting up a single IMAP account on multiple computers, try taking a break between each setup.

Set up IMAP

Step 1: Check that IMAP is turned on

1. On your computer, open Gmail.
2. In the top right, click Settings .
3. Click Settings.
4. Click the Forwarding and POP/IMAP tab.
5. In the "IMAP Access" section, select Enable IMAP.
6. Click Save Changes.

Step 2: Change SMTP & other settings in your email client

Use the table below to update your client with the correct information. For help updating your settings, search your email client's Help Center for instructions on setting up IMAP.

Read Gmail messages on other email clients using POP

You can open your messages from Gmail in other mail clients that support POP, like Microsoft Outlook.

Step 1: Make sure POP is the best way to read your emails

IMAP and POP are both ways to read your Gmail messages in other email clients.

IMAP can be used across multiple devices. Emails are synced in real time.

POP can only be used for a single computer. Emails aren't synced in real time. Instead, they're downloaded and you decide how often you want to download new emails.

Step 2: Set up POP

First, set up POP in Gmail

1. On your computer, open Gmail.
2. In the top right, click Settings .
3. Click Settings.
4. Click the Forwarding and POP/IMAP tab.
5. In the "POP Download" section, select Enable POP for all mail or Enable POP for mail that arrives from now on.
6. At the bottom of the page, click Save Changes.

Next, make changes on your email client

Go to your client, like Microsoft Outlook, and check these settings.

There isn't one. Google doesn't make one. You can use your browser or Apple Mail or a different email client.

Just to add, there are "Gmail" apps in the App Store. None by Google and I have no idea if any of them are worth installing. Just do a search on the App Store for "Gmail".