Beginner - Line art question

Although the image above is not not a line art image, the "Blend If" option described below still applies.

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If there is a lock on the background layer holding the image, drag the lock to the trash.

Place a transparent layer below the image layer

Double click on the image layer to bring up Layer Style

In the Blend If section, gently move the right slider to the left until the uneven white surround disappears.

Layer > Merge Down the image and save as a psd file. (If you save as a jpg, the white will return.)

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If you have Adobe Illustrator you will find it will help you get the desired result and deliver vector result, which you may prefer.

Try this Line Art Photoshop Action; it will remove the background for your line art or sketch

https://www.photoshopsupply.com/actions/line-art-photoshop-action-free

From these appends you should see that there are more that one way to do something using Photoshop features.

I'm not artiest but to it its seem what you want to see is your line art and not the background you drew it on,   The first beginner mistake you made was you drew on the background.  Photoshop's Power lies in layers and selections.  Try to remember that.  What you should had done was.  Add an empty layer on top of the background layer and draw.  That way your drawing would be on its own layer not in the background layer.  Remember I wrote  Power = Layers + Selections.   A selection may be able to made that can lift your artwork off the background layer and put it on its own layer.  You art will be on two layer then.  Its layer and your Background layer. You can than delete the background layer. Have only your art.  You should try doing that.

A very simple way to do this is with the Levels command (Menu: Image/Adjustments/Levels). This adjustment allows you to set the Black, White and Mid points of your image. In your case you want to make the undesired not-quite-white values turn white.

Slide the White Level pointer to the left until all of the undesired values have turned white. If you then need to beef up your line work, slide the Black Level pointer to the left.

Try: Image > Adjustments > Levels and adjust the Input Levels to lighten the background.

P.S. Don't worry about asking questions here!