To send cryptocurrency offline, you will need two computers, one of which is not connected to the Internet.
Go to the MEW github profile (https://github.com/kvhnuke/etherwallet/releases) to download the local version to your PC (etherwallet-v3.40.0.zip).
Detailed MEW instructions offline
Signed transaction generation offline:
1) On a PC with Internet access, go to MEW (unzip the previously downloaded archive and run index.html).
2) Click on the “Send Offline” tab
3) In the “From Address” field, enter the number of your wallet from which the cryptocurrency will be sent, and click “Generate Information”.
4) We will be shown the values of "Gas Price" and "Nonce", which you need to remember.
5) On a PC where there is no Internet, run index.html.
6) Click on the “Send Offline” tab in the “From Address” field, enter the number of your wallet from which the cryptocurrency will be sent.
7) In the “To Address” field, enter the number of the wallet to which the cryptocurrency will be sent. In the “Value Amount to Send” write down the amount of cryptocurrency sent.
8) The Gas Limit field is set automatically. When sending cryptocurrencies, Gas can be increased and paid from ETH.
9) Fill in the fields “Gas Price and Nonce” based on paragraph 4).
10. The "Data" field remains empty.
11. In the field “How would you like to access your wallet?” Select “Keystore File (UTC / JSON)” add the saved file and enter the password.
10. Click "Unlock" then click "Generate Transaction". Copy the value of "Signed Transaction".
Sending a finished transaction to the network:
1) On a PC with Internet access, run index.html.
2. Click on the “Send Offline” tab, in the “Signed Transaction” field, insert our finished transaction and click on “Send Transaction”.
Thus, the transaction is offline. The point is that you are not showing your private key anywhere, only a ready-made transaction gets to the Internet, in which it is impossible to decrypt your private key.
This is one of the safest ways to work with your MEW wallet. More powerful protection is achieved by using hardware wallets.