When you have created a campaign, you can invite creators to join it. Under "Discover" you can easily find and invite creators. You can filter for relevant creators by clicking on the various filtering options at the top of the page.
Once you have found a relevant creator, you can invite them to your campaign, by checking them off in the view as shown below.
First, you select your campaign. And then you search for the creators you'd like to invite to your campaign using the filters. Once you've found the creators you want to invite - click "Recruit influencers" in the left-hand menu. This will open a menu allowing you to select their compensation and write a message.
You have the option to invite multiple influencers at once. Here, you need to select the ones you want to invite, personalize the invitation message by using their first name and write a good invitation message, as seen above. You also have the option to customize the commission for each individual influencer, in case you want to give a higher commission to a larger influencer or one you have collaborated with before. The other influencers will not be able to see if you increase the commission for a specific influencer.
Before you start searching for new creators, it's a good idea to check your campaign applications - you may already have creators wanting to collaborate with you.