Assign a member to a card

I’m trying to assign a member to a card after create it with CURL and PHP, but i can’t find the right URL. I tried with:[card]/idMembers?idMember=[idmember]&key=[key]&token=[token]

but does not work. In [idmember] i tried a lot of combinations like the “id”, the “fullname” or the “username” but neither works. This is the response i have when i get the members of one specified card:

[{"id":"xxxxxxxxx","activityBlocked":false,"avatarHash":"---","avatarUrl":"", "fullName":"FullName","idMemberReferrer":null,"initials":"J","nonPublic":{},"nonPublicAvailable":true,"username":"UserName"}]

What i am doing wrong?

Thank you in advance.

Sending data with CURL. Solved.