How to rename all column names in tibble by passing a character vector?

I have a tibble named X of multiple columns (over 500) which are named in format of "X"+integer. The tibble looks like this.

# A tibble: 7,352 x 561
      X1       X2     X3     X4     X5     X6        
    <dbl>    <dbl>  <dbl>  <dbl>  <dbl>  <dbl>  
 1 0.289 -0.0203  -0.133 -0.995 -0.983 -0.914 
 2 0.278 -0.0164  -0.124 -0.998 -0.975 -0.960 

The txt file didn't contain column names, but they are in another txt file which I have read into another tibble. This tibble is size of 561x1.

What I wanted to do is to rename all of the column names of tibble x by using row values (=converting the tibble to character vector named y).

I have tried dplyr function rename_all without a result.

Here's an example which I believe is quite close to actually working, but I don't quite understand how to work with function list

> rename_all(x,list(paste0(y)))

The above command in RStudio command line produces following error message:

Error in get(.x, .env, mode = "function") : 
  object 'tBodyAcc-mean()-X' of mode 'function' was not found

The tBodyAcc-mean()-X is the value in the first row of character vector y.

I have tried to googling the error message, but so far I have no idea what is causing that and how should I modify the rename_all command to get it working.

Any help is much appreciated!