There are a number of forum threads with tips and suggestions for ways to get started as an IDer – e.g., this recent one (and the linked threads).
As for where to start – wherever you want! Sometimes the forum discussions make it sound complicated, but there isn’t really any one best way to approach IDing. I think a lot of people try out a variety of different things before figuring out what they enjoy IDing and what workflow is most satisfying for them.
I started IDing because around the time I joined iNat, there was a school project that resulted in a lot of observations of daffodils ID’d as primroses and similar mix-ups and I realized that there were some common organisms that I recognized and I could help correct these observations. So browsing observations in your area and seeing what you can contribute can be a good way to get started.
Or pick something that interests you and you want to learn more about – or something that you feel like you are reasonably confident recognizing in your own observations (if, say, odonates all look more-or-less alike to you, this may not be the best place to start; but if you see them and think, this is a damselfly not a dragonfly, or I recognize that pattern of markings, you have a good intuitive basis that you can build on). Ideally I would suggest choosing something where there is not already a surfeit of IDers (i.e., maybe not birds and other vertebrates unless there is something you are really passionate about).
It is not necessary to provide a species ID all the time. Lots of observations get entered with no ID or a broad ID and if you can refine the ID – that insect is a butterfly – you will increase the likelihood that the observation will be seen by an expert who can take it further. A nice side-effect of this is that you then get to see subsequent IDs for the observation, and maybe over time you will be able to take the ID further yourself.
(I find that I can provide more useful IDs in regions where I am somewhat familiar with the flora and fauna, but I think some users enjoy the opportunity to virtually explore far-away places and discover unfamiliar organisms.)
I find it helpful to go back at least a day or two so I don’t feel like I am competing with other IDers for the most recent observations. You can also filter your search for observations that only have a broad ID, or only observations by new accounts, etc.
It is OK to make mistakes. As a new IDer it is often a good idea to not suggest species IDs unless you are pretty certain of the ID and know that there are no lookalikes, but for broader IDs it is fine to suggest an ID that you think is likely even if you aren’t totally confident about it. And if you get it wrong (say, the “butterfly” turns out to be a caddis fly instead), it is not a big deal, as long as you follow your notifications and withdraw your ID if necessary.