I assume you mean your RPi hostname.
From the first menu choose option 8 (Advanced Options)
From the Advanced Options menu choose A2 (hostname)
Read the rules then press enter to get to the hostname entry panel
On there give your RPi a new name. Then choose OK to complete the rename.
Note: Any requirement to use a crystal ball or mind reading will result in me ignoring your question.
Criticising any questions is banned on this forum.
Any DMs sent on Twitter will be answered next month.
All fake doctors are on my foes list.