# Burn Window
To join a whitelist sale and purchase tokens for IDOs on StarLaunch, you'll first need to secure an allocation by burning Hydrazine ($N2H4) within this window of time (usually 2 days).
At the [Sale Details](https://app.starlaunch.com/sale-detail) page, connect your KYC-approved wallet. If you're [eligible](/starlaunch-a-cadets-guide/launch-events/kyc-process.md), you'll see an input field you can use to burn $N2H4.
Under "Individual Limit" you'll see the maximum amount of $N2H4 you can burn for this IDO. Read [Calculating Allocations](/starlaunch-a-cadets-guide/the-basics/two-token-mechanics/calculating-allocations.md) to learn how this is determined. When you're ready, enter the amount of $N2H4 you'd like to contribute and click **BURN**.
Once you complete the transaction, you'll see your amount burned next to "Your Contribution." Remember, you can burn multiple times during the burn window to increase your contribution.
You'll notice the dashboard doesn't yet say how much of the project token you'll be able to purchase. Because allocations are distributed proportionally according to $N2H4 burned, this number is calculated at the end of the burn window.
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