Your Myplace profile is based on the details held in your PEGASUS Student Record, and must be changed there.
I don't want my middle name(s) to appear in Myplace
Depending on the information held in PEGASUS, your middle names may be held such that Myplace receives them as part of your forename.
You may be able to update this information in PEGASUS directly, otherwise you should speak with Student Business about updating your Student Record.
If you hold a Tier 4 Student visa you will need to speak with Student Business to update yourname (see I can't change my name on PEGASUS below).
I can't change my name on PEGASUS
You may find that if you hold a Tier 4 Student Visa you cannot update your name on PEGASUS as the University must hold your name as it appears on your identification documents.
However you should be able to speak with Student Business directly, with evidence from your ID documents and they can record this, and amend your first, middle and surnames appropriately.