reran lts 22 installer - could not alter prior partitioning

[Robert Moskowitz]

I am new to Ubuntu.  I have decades with CentOS and Fedora, so am use to 
their installer where I run ext4 without LVMs.

I had to reinstall Ubuntu, as I messed up the install of Mail-in-a-Box 
(I know too much for my own good, it seems) and the easiest path was 
starting over.

I did not "like" what the Ubuntu installer did.  I have a 500GB SSD 
drive, and it only allocated 100GB to the / partition.

This Zotac Zboxnano has 2GB memory and I replaced this original HD with 
said SSD drive.

In /etc/fstab there is:

/dev/disk/by-id/dm-uuid-LVM-Of0ciG9Rj2oEXQTBmqvSYhxN750GH9QTckCCW3W0nXsNN3J7fji735bWG831VRKD 
/ ext4 defaults 0 1
# /boot was on /dev/sda2 during curtin installation
/dev/disk/by-uuid/62887e8e-6dea-4bcc-a830-a9ec367fe578 /boot ext4 
defaults 0 1
/swap.img    none    swap    sw    0    0

and df reports:

Filesystem                         Size  Used Avail Use% Mounted on
/dev/mapper/ubuntu--vg-ubuntu--lv   98G  5.1G   88G   6% /
/dev/sda2                          2.0G  126M  1.7G   7% /boot

I want to "grow" the partition with /

How do I do that, since I could not figure out the custom drive 
installer to change that original install and let me make it use more of 
the drive (there is some 300GB free in the LVM partition right now).

thanks