To encrypt a flash drive, you can use a feature called BitLocker or BitLocker To Go. You can find this feature by right-clicking on the flash drive in File Explorer or in the Settings app under System > Storage > Advanced storage settings > Disks & volumes. You need to choose a password to unlock the drive. The steps may vary slightly depending on your Windows version.

Here are the steps to encrypt a flash drive with BitLocker :
1. Insert the flash drive and launch This PC/My Computer.
2. Right-click the drive and select Turn on BitLocker.
3. Click on Use a password to unlock the drive.
4. Create a hard-to-guess password and enter it in the textbox.
5. Save the recovery key in a secure location and then click Next.

You can also encrypt your USB flash drive using Norton :
1. Choose which filesystem you want to use — NFTS, exFAT or FAT32 — by right-clicking.
2. Encrypt your flash or external drive by selecting the drive in your file explorer, hitting your Manage button and selecting “Encrypt”.
3. Enter a strong password to keep others from gaining access.