I am using the Connect App, currently version 6.5.0 on my Android phone, and here is how to create a group within the app. If you do not currently have the contacts you want in the new group already setup, do so before proceeding on as the create group process needs the contacts setup before you create the group.
With the app open, select the three horizontal lines in the upper left hand corner to open up the menu of options and select Contacts. When the Contacts screen opens up, if you have the options of Phone and Xfinity, select Xfinity. On the top bar where the menu option and Contacts is, select the big + sign and from the fly out menu select New Group. On the box that opens up, input your new group name and select OK to save it.
After selecting the OK option to save the group name, you are taken to a listing of your contacts to select which ones you want in the group. Select the square box to the right of each contact name you wish to include in the new group and when done select the Create Group at the bottom of the screen. At least for me, after the group was saved I did have to use the refresh option, a circle composed of two curved arrows, before the new group showed up.
With the new group now showing, select it and then from the new screen you can select the Email Group option which will open up the email screen where you can composed your email to the group and send it.
Regarding sending Text Messages to the group, based on my own observations it does not look like the texting function utilizes the groups that you create and can use in the email function. I say this because when I open the Connect App, select the three horizontal line option in the upper left hand corner of the screen to open up the menu and select the Text option, when on the Text screen and select the Text icon in the lower right hand corner of the screen to get the actual compose text screen to open up, on the To line I select the + sign to open up my Contacts list and the groups I have are not there, only the individual contacts. Within this list of individual contacts I can select multiple contacts to send the text to and it will send a text to multiple contacts but I have observed that this seems to be individual texts as when one recipient replies back only I can see their reply, none of the others that received my text can see that reply. I do not think this is a limitation of the actual Connect App itself as it is more of how the text system works in general as the same thing happens when I use the web page text function. Of further note, if I happen to be in the Contacts area where my groups are listed and I select a group, I only have an option to email the group, I do not have an option to text the group.