How can I fix a circuit where the outlet tabs were erroneously removed?

The reason those tabs are removed is to have one outlet always hot and the other outlet switched hot. That way, you can plug a lamp into the switched outlet and turn a light on from the doorway.

If you purchased outlets with a side-screw connection that does not require bending a shepherd's crook into the end of the wire, (these are often on the "commercial" grade outlets and are well worth the extra buck or two for the convenience), you can back the screw out, loosening the clamp, then put a jumper from the top screw to the bottom screw and tighten everything down.

If you purchased "standard" grade outlets that required looping the wire around the screw, you can run your hot to a pig-tail, then have 2 tails come out of it - one to the top outlet and one to the bottom. You can do this 2-pig-tail method with the "commercial" grade outlets, too - the choice is yours.

You could, of course, chuck all the outlets you just did, replace them with new ones, and chalk it up to a learning experience, but even for the $1 cheapie "standard" outlets, that's not really necessary.

As noted in the comments, please do not use the "backstab" connections. These allow you to push ("stab") the wire straight into the back of the outlet and hold the wire with an internal spring clamp, not a screw. These have a tendency of working loose over time allowing the wire to come out (at a minimum) or causing arcing and a fire (at worst). They are legal (code approved), but very much not recommended.

The tab on duplex outlets connects the top and bottom electrically. As you'll note, standard outlets have two screws for each of hot and neutral. The reason there are two screws is so that you can choose to break the tab and have them powered independently of each other. The purpose of powering them independently can be two fold. One purpose would be so that one outlet is switched while the other is always on. Another reason would be so that each is on a different circuit (for load balancing purposes). In either case, when you break the tab it means that you have to use both pairs of screws to get power to each outlet.

As @Freeman already said, if you break the tab but still want to have both outlets electrically connected, you have but to make a pigtail (splice in the same box) so that you can connect a hot wire to each of the hot screws. You will not need to do this on the neutral side if you didn't cut that tab.