To login you need to make POST request to
https://bsky.social/xrpc/com.atproto.server.createSession
with JSON in body
{
"identifier" : "alice.host.com",
"password" : "PASSWORD"
}
then you get like this
{
"did" : "did:plc:121344",
"handle" : "alice.host.com",
"email" : "email@mail.com",
"accessJwt" : "accessJWT",
"refreshJwt" : "refreshJWT"
}
Then you can use this JWT Token as Bearer authentification when you are making requests that needs auth