Most of telegram bots require admin privilege to work properly in chat group.
If you use telegram desktop client.
Go to your group. Click on group's title. Group Info window will be opened.
Click on three dots icon (left off cross icon in top right corner of window) and choose "Manage group" item in menu.
Click on "Administrators" item. Administrators window will be opened.
Click on "Add administrator" button. Add Administrator window will be open.
In the text input field with magnifier icon input EXACT username of bot. Do not input part of name, type FULL EXACT username of bot. If you do not do that you might add incorrect bot into group. For example, if you want to add daysandbox bot, do not enter "DaySandbox", "daysan", "Day Sandbox". Use only full bot's username: "@daysandbox_bot".
In search results click on first item. Edit Permissions window will be opened.
Required permissions depends on exact bot and are documented in bot's documenation at tgdev.io website. You can just grant all permissions to bot - that will be enough.
Now click SAVE button. It might say you that the user is not member of the group. This is standard telegram security message. Just click "OK" button.
Congratulations, you've added bot into your group.
Now read documentation and find out if you need to do additional actions to configure bot. Each bot is documented at tgdev.io website.