You cannot upgrade your MT4 trading platform to MT5.
If you like to have the MT5 trading platform, you will need to install the MT5 trading platform on your device directly.
To get an MT5 account, add an additional MT5 account from your dashboard using the procedure below:
First login to your client portal via: https://portal.fxpesa.com/#/auth/login
and on the accounts section on your dashboard, Click on ''CREATE ACCOUNT'' as highlighted on the screenshot below:
Then proceed to select the platform type, which is Metatrader 5 as indicated on the red arrow on the screenshot below:
Finally, login into your MT5 trading platform using your new login credentials.