After logging into Asklayer, click on your user name at the top right of the screen and select 'Profile' from the drop down menu.
Next, click 'See plans' in the 'Your plan' section.
In the next window, locate and click 'Select plan' on the plan you wish to upgrade to.
After selecting your desired plan, click 'Yes, change it' in the confirmation window to proceed to the billing section.