"To find a teammate" means to discover and connect with someone who can work with you, support you, and collaborate with you on a task or project. Full definition
He's creative without being careless, showing an innate ability to find teammates thanks to his special combination of vision and height. (sbnation.com)
The other side of finding a teammate is being a teammate in return. (edutopia.org)
The fastest way to play is to have a full 5 person party before looking for a match since you won't have to find any teammates beforehand. (thatvideogameblog.com)