A bear call spread is a options trading strategy that involves selling a call option with a higher strike price and buying a call option with a lower strike price on the same underlying asset, with the same expiration date. The goal of the bear call spread is to profit from a decline in the price of the underlying asset, or to generate income from the premiums received from selling the call options.

In a bear call spread, the trader sells the call option with the higher strike price and collects the premium from the buyer. At the same time, the trader buys the call option with the lower strike price and pays a premium to the seller. The trader is hoping to profit from the difference between the two premiums, as long as the underlying asset stays below the strike price of the call option that was sold.

However, there is also the risk that the underlying asset will increase in value, in which case the trader may be required to sell the underlying asset at the higher strike price to the buyer of the call option. This can result in a loss for the trader.

To implement a bear call spread using the Zerodha or Upstox trading platforms, you will need to follow these steps:

1. Log in to your account on the Zerodha or Upstox platform and navigate to the options trading section.

2. Select the underlying asset that you want to trade and choose the expiration date for the options that you will be selling and buying.

3. To create the bear call spread, you will need to sell a call option with a higher strike price and buy a call option with a lower strike price. You can do this by clicking on the "sell" button for the higher strike price option and the "buy" button for the lower strike price option.

4. Review the details of your trade, including the premiums that you will receive and pay, and confirm the trade if you wish to proceed.

It's important to carefully consider the potential risks and rewards of the bear call spread strategy before implementing it, as it is a potentially risky strategy. It's also important to have a good understanding of the underlying asset and the market conditions that may affect its price.