give permissions to a file

the command is

chmod 777 file

The first digit (7) refers to the permissions of the file owner.
The second digit (7) refers to the permissions of the group to which the file belongs.
The third digit (7) refers to the permissions of other users.

perhaps it is run with superuser permissions, that is, with sudo.

Permissions can be represented as follows:
0: No permissions
1: Execute permission
2: Write permission
4: Read permission
5: Read and execute permission
6: Read and write permission
7: Read, write and execute permission

777: Read, write and execute permission for all users.

view all files in a directory and their permissions:

ls -l