First make sure that you have the game downloaded and have played it at least once (you probably have) and go to your windows settings
https://steamuserimages-a.akamaihd.net/ugc/2314349699957130577/180A325C2A739C3C57993471F1701475ACD40AAF/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false
Next, go to display settings
https://steamuserimages-a.akamaihd.net/ugc/2314349699957144747/28DFF9FA0601F65DAA7753E4965371A6BA39DC0B/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false
Once you're there, scroll down until you find "Graphics"
https://steamuserimages-a.akamaihd.net/ugc/2314349699957152773/5F9B72C1A22FE15CC3EF6BA2296491445A8EB376/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false

Once you're here, scroll down to see if Borderlands Game of the Year Edition is there, if not click the drop down menu under "Add an app" at the top, and make it "Desktop app" and then click "Browse"
https://steamuserimages-a.akamaihd.net/ugc/2314349699957174501/50429BD439CBF96BE3290BADFE65BC07F22A7C15/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false
Going though your files, find where you installed steam and go into the folder for it (I have an external hard drive so I click into that and into the steam folder)
https://steamuserimages-a.akamaihd.net/ugc/2314349699957184706/6F4119825C544388738E63D0AA0B8098E4DAF5A2/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false
Scroll until you see "steamapps" and go into the folder
https://steamuserimages-a.akamaihd.net/ugc/2314349699957189644/86CEB9AD6098F2FA3216087895B3F3D69BBC4C50/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false
At the very top, you should see the folder "common". Go into that folder and then go to "BorderlandsGOTYEnhanced"
https://steamuserimages-a.akamaihd.net/ugc/2314349699957189644/86CEB9AD6098F2FA3216087895B3F3D69BBC4C50/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false
https://steamuserimages-a.akamaihd.net/ugc/2314349699957203940/B8011D08A8AA8FE5FD33EA9882C742FC4E0D0C0B/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false
Go to "Binaries" and then "Win64"
https://steamuserimages-a.akamaihd.net/ugc/2314349699957212070/5065134F3611F6C8B31ED29608E79D21EA10970D/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false
https://steamuserimages-a.akamaihd.net/ugc/2314349699957214239/8DC53CF49951CD0DA7C0C87B87F593F7A2921076/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false
Once you're here, you should see it, if not scroll for the item "BorderlandsGOTY" with the borderlands GOTY enhanced logo next to it
https://steamuserimages-a.akamaihd.net/ugc/2314349699957220193/2DA682F73EB4CF5FF9B1B2444DE58685C2EEBC01/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false
Then click "Add" in the bottom right corner
https://steamuserimages-a.akamaihd.net/ugc/2314349699957225334/B90BE427D1739073308B9EDA89D3648140451152/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false

Now that you did that step, it should be added now into the graphics menu if it wasn't there before.
https://steamuserimages-a.akamaihd.net/ugc/2314349699957237484/30B6D7E5F71F0D72BA9C7187EE95B20B8A9244E5/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false
To get that menu below it (if it wasn't there already) click on it, and then click options, and then click "High preformance" and then click save.
https://steamuserimages-a.akamaihd.net/ugc/2314349699957243905/B65CE0CDF8EB0219984609F44C616936513D9AC9/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false
After that your game should run smooth now.

this is me when i get steam points and awards from you
https://steamuserimages-a.akamaihd.net/ugc/2314349699957254374/912FC2904ABE582E3B44F566DC50487A97BA394C/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false