See this page for more details on how to install vsftpd:
https://help.ubuntu.com/community/vsftpd

Run the following command to install vsftpd:

$ sudo apt install vsftpd

Notes:
The user 'ftp' and the group 'ftp' will be created.
Also, the folder '/srv/ftp/' will be created.

Create an ftp administrator user:

$ sudo useradd admin1
$ sudo passwd admin1

$ sudo usermod --home /srv/ftp/ admin1
$ sudo usermod -s /sbin/nologin admin1

$ sudo usermod -a -G ftp admin1

$ sudo chmod 775 /srv/ftp

Modify the following settings in the file '/etc/vsftpd.conf' to enable write permissions:

$ sudo vi /etc/vsftpd.conf

write_enable=YES
local_umask=022

To allow just some users to login to the server, add the following settings in the file '/etc/vsftpd.conf':

$ sudo vi /etc/vsftpd.conf

userlist_deny=NO
userlist_enable=YES
userlist_file=/etc/vsftpd.allowed_users

Create the file '/etc/vsftpd.allowed_users' and add the username of the users that can login to the server:

$ sudo vi /etc/vsftpd.allowed_users

admin1

Use FTP to connect to the server:

$ ftp localhost

You need to type your username and password:

Connected to localhost.
220 (vsFTPd 3.0.3)
Name (localhost:mtitek): admin1
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp>

ftp> pwd
Remote directory: /srv/ftp

You might get an authentication error when trying to connect to the server.

$ ftp localhost

Connected to localhost.
220 (vsFTPd 3.0.3)
Name (localhost:mtitek): admin1
331 Please specify the password.
Password:
530 Login incorrect.
Login failed.
ftp>

If so, comment the following settings in the file '/etc/pam.d/vsftpd':

$ sudo vi /etc/pam.d/vsftpd

#auth   required        pam_shells.so