Like anything start slow and work your way to be getting faster and faster.
At the same time also concentrate on where all the notes are all over your fingerboard.
Sight reading comes from practice 'til one acheives fluency between what is written on the page and, with time, knowing where on the fingerboard is the most comfortable/economical to play the line.
As your sight reading gets better you will be actually be reading a little ahead of what you are playing, so you can decide what fingerings are going to be most economical getting to the next passage.
Knowing the fingerboard is key.
My fave bass book vv: Have fun!



https://www.shermusic.com/0961470100.php
At the same time also concentrate on where all the notes are all over your fingerboard.
Sight reading comes from practice 'til one acheives fluency between what is written on the page and, with time, knowing where on the fingerboard is the most comfortable/economical to play the line.
As your sight reading gets better you will be actually be reading a little ahead of what you are playing, so you can decide what fingerings are going to be most economical getting to the next passage.
Knowing the fingerboard is key.
My fave bass book vv: Have fun!


https://www.shermusic.com/0961470100.php