In Microsoft Teams only a Team owner can add/remove members.  Members can submit a request which will go to the owner for approval.  

To add members to a team:

  1. If you're a team owner, go to the team name in the teams list and click More options More options button > Add member.
    Add members to a team in Teams

  2. Start typing a name, distribution list, security group, or Microsoft 365 group to add to your team. 

  3. When you're done adding members, select Add. Fyi, you can make someone a team owner by selecting the down arrow next to the word Member. There can be multiple owners in a team. 

  4. Select Close. People you add to a team will receive an email letting them know they are now a member of your team and the team will show up in their teams list.

To remove members from a team:

  1. Go to the team name and then click More options More options button > Manage team > Members.
  2. From your team member list, click the X to the far right of the name of the person you'd like to remove.
    1. To remove another team owner, first change their role from owner to member, then remove them.
  3. Once you remove someone from a team, you can always use Add member to add them back to the team later on.