Your anchor desktop should look like this. Click on Settings (top left)
Change this to Display Advanced Settings.
Now we see this.
Generate a Public / Private Keypair
For advanced users, you can generate keys in in Anchor, or using the Ian Colman Utility - check out the Cryptographic Keys section of these docs for more info.
Copy the Public Key and Private Key from here - green and red sections below. Blue and brown sections are optional for testnet and may be confusing to save.