In order to get your Stripe API keys you first need to create a stripe account and then go to: https://dashboard.stripe.com/.
Here you can then click on "Developers" and then on "API-keys":
Now you need to make sure, that you are in "Live mode".
You can toggle the mode in the upper-right corner.
If you can not set your toggle to Live mode, it means that your account setup is not complete yet. If that's the case just click on the link and follow the instructions:
Once your setup is complete, you will be able to go to Live mode. Please note that once you have entered all the data, it can still take up to a couple of workdays for Stripe to fully activate your account.
When your account is activated, you will find, that your API keys start with pk_live_ and sk_live_ respectively. To view your secret key (and therefore also to copy it), you need to click on "Reveal live key".
You will be warned, that it can only be revealed once. You can ignore the warning, but keep in mind that you need to copy the key, before hiding it again.
In order to copy the keys you can just click on them and they will be copied to your clipboard.
Once you have your Publishable key (starting with pk_live) and your secret key (starting with sk_live), you can return to the payment settings (https://app.rentware.io/settings/payment) and enter them in the Provider settings.