Ubuntu Studio would be located on a different partition. This could be on the same HDD where you want more space, but it's possible that you installed it somewhere else (if you had space on another disk).
You can probably just delete the partition where Ubuntu Studio was installed, but this will not automatically free up space on your hard drive if Ubuntu Desktop 20.04 is located on the same drive. (Please accept my apologies that I'm not familiar enough with the MacBook hardware to know if it could contain multiple hard drives, but my best guess is that it only has one)
Since these are both new installations and you told us that you are new to Ubuntu, it's probably easier to reinstall Ubuntu Desktop 20.04.
You can prepare your hard drive ahead of time with the "Disks" application in the live session (Try Ubuntu), by choosing the disk and selecting "Format..." This will erase the hard drive so you have a clean slate to install Ubuntu. This might be a better path if you have multiple hard drives, so you can prepare the correct drive. Be careful and choose the right disk because formatting will erase whatever disk you choose. When you are asked for a partition scheme, GPT is generally the better choice for a modern OS.
Alternatively, and especially if you only have one hard drive, you can just start the installation and when you are asked for the destination where to install Ubuntu, you can choose the option to Erase the Disk and install Ubuntu. This will use the entire hard drive for the installation.
