I can only edit images when my sd card is in, when out it says file cant be found

Sounds like you made the following mistake: When you insert an SD card and import the images into Lightroom, Lightroom will tell you it needs to copy the images to another location. You choose that location in the right panel. Contrary to what @KR Seals suggested, you cannot choose 'ADD' by mistake, because that option will be dimmed with memory cards, to save you from making that mistake. Unfortunately there still is a way to effectively do the same: If you choose the same SD card as destination, then the copied images that Lightroom uses will still be on the SD card, and so they will be 'missing' if that SD card is not mounted. You need to choose a location on a hard drive!

The current situation can be fixed, but may need a work around. Please post a screenshot of Lightroom in Library view, showing the folder panel. We can tell you how to fix it if we can see the current situation.

We will need more information. 

Where is the card located? In the camera, a reader?

It sounds like you may have imported the photos on the card with the "Add" selection at the top center of the import dialog. The correct choice in that situation is to "Copy" the images to a drive on your computer. When you choose "Add", you then need to use the panels at the right hand side of the screen to tell Lightroom Classic where to put the images on you computer drive.

Does that help? Look up some videos on "Importing" in Lightroom Classic.

Here is an Adobe Video that explains importing.