Technical requirements
Before you start creating Log Analytics workspaces and using Microsoft Sentinel, you will need to set up an Azure tenant and subscription. It does not matter what type of Azure tenant you have, if you have one that you can use. If you do not have access to an Azure tenant, you can set up a free trial by following the instructions at https://azure.microsoft.com/en-us/free/.
Once you have a tenant, you will need a subscription as well, if there is not one that you can use already. Depending on the type of Azure tenant you have access to, you may need to contact someone else to create the subscription. If you need help creating a new subscription, go to https://docs.microsoft.com/en-us/azure/cost-management-billing/manage/create-subscription.