Open the message you want to reply to or forward.
On the message header, tap the Reply icon ,
or the Forward icon
.
Add others to an ongoing conversation by replying to all and then adding the new person’s address(es) to the reply.
Tap the Send icon at the top right
corner of the screen to send your Gmail message.
You can
change the message action after you've started the message. Simply
tap in the
upper-left corner (next to the current message action), then tap the
one you want. For example, if you chose Reply but decide you want
to Reply all instead.