To find the make, model and IMEI number of a phone via your My.plan log in, look in the CARDS section for the user in question and click on their USER NAME LABEL > CONNECTION DETAILS.
Your phone's IMEI number can be accessed by dialling *#06# The IMEI will pop up on the screen. This method isn't universal, however.
Your phone's IMEI number will be displayed on the box the phone came in.
In most older model phones, the type with a removable battery, the IMEI can be found on a sticker under the battery.