You can purchase a subscription for XMind for iOS from App Store.
1) Launch XMind for iOS,
2）Go to Settings > Unlock full version，
3) Select the subscription you want to buy，
4) Sign in with your XMind account,
5) Enter purchasing page to pay for the subscription.
How to unlock full version of XMind for iOS after you pay for the subscription?
After you purchase the subscription, you can follow these steps to unlock full version.
1. Launch XMind for iOS,
2. Go to Settings > Sign In,
3. Enter your XMind ID and password,
4. Then you can unlock the full version for XMind for iOS.