how do i increase storage on my MacBook Air?

Which MacBook Air do you have?

If it is an old model with a hardware release year between Late 2010 and 2017 (as shown in the About This Mac dialog in the Apple () menu), you may be able to replace the internal SSD with a larger aftermarket one. (See: Other World Computing – SSDs for MacBook Air)

If it has a hardware model year of 2018 or later, the SSD is soldered in, and there is no way to upgrade it. You can only try to free space, and/or add external storage.

AngelicaRG wrote:

I'm having a hard time increasing my storage. An external hard drive isn't working. and I can't even update my IOS.

Here are the instructions for freeing up storage space: Free up storage space on Mac - Apple Support

AngelicaRG wrote:

I can't even update my IOS.

Whether and how far you can upgrade macOS will depend on the hardware model year of your MacBook Air. What does it say about that in the About This Mac dialog in the Apple () menu? (No serial numbers, please.)

Note that Macs run macOS – not iOS.