You have two things to get used to.
A new bass
and
another string.
Use the fat string for a thumb rest until you feel at home on the new bass.
Once you are comfortable then start exploring the B string.
The thing I did that opened my eyes was to play something in E that you have always used the open E string for, play it a couple of times then use the 5th fret E on the B string.
WOW!
Presto chango! You are now playing across instead of up and down the fretboard.
Once you feel the power, depth and ease of playing you'll love 5 string.
It can also help some if your 4 string and 5 string use the same string spacing.
A new bass
and
another string.
Use the fat string for a thumb rest until you feel at home on the new bass.
Once you are comfortable then start exploring the B string.
The thing I did that opened my eyes was to play something in E that you have always used the open E string for, play it a couple of times then use the 5th fret E on the B string.
WOW!
Presto chango! You are now playing across instead of up and down the fretboard.

Once you feel the power, depth and ease of playing you'll love 5 string.
It can also help some if your 4 string and 5 string use the same string spacing.