As a B2B SaaS startup, how did you get your first 5 users

Having this same issue. I originally was running cold email campaigns to potential customers but was getting no luck. Some good advice I have received is that early on you have to do things that do not scale. You are going to have to put in a lot more work to get your first customer then you will have to to get your 100th. So (depending on the product) forget about stuff like cold outreach. Join communities and participate in conversations. Go to an in-person event relevant to your industry. Build a strong relationship with that first customer. Utilizing your personal network is a good way to achieve this.